Grant River, is navigable fourteen miles, from Cambridge to its mouth in the Great Ouse at Harringore, above Ely. It is embanked above the fens in all its lower parts, and has sluices for making flashes of water, to enable boats to pass the shallows. There is a cut of three miles from it to Rehe, and another of three miles and a half to Burrell.

iver is navigable from Guinea Port, near Wade Bridge, to the sea at Stepper Point, three miles east from Padstow, in the Bristol Channel, a distance of eight miles and a half by the low-water channel.

The Canterbury Navigation, or river Stour, from the city of Canterbury to the Downs at Sandwich Haven, having been very imperfect and inconvenient, an act was obtained in 1825 for making various improvements on it; particularly a canal or harbour eight feet deep, from the Small Downs, commencing between the Batteries No. 1 and 2, to the river Stour at Sandwich, which is to be two and a half miles in length from the end of the proposed jetty of 1000 feet next the Downs; thence the navigation is continued in its old course sixteen miles to Fordwich, where there is a lock of six feet lift. From this to the tail of Abbots Mill, Canterbury, the length is two miles and a quarter, including three short cuts amounting together to one and a quarter mile. There is another lock of six feet lift half a mile from Canterbury. The total length is twenty miles and seven eighths.

anal, see Glamorganshire.

Carlisle Canal proceeds north-west from the west side of that city, and twice crossing the line of the Picts' Wall, continues by Kirk-Andrews to Wormaldy, taking a westerly direction along the south side of the Picts' Wall, by Burgh; thence crossing the marshes, and passing by Drumburgh Castle and Glasson, it enters the Solway Frith at Fisher's Cross near Bowness. It is eleven miles and a quarter long, descending seventy feet by nine locks.

iver, Stirlingshire, is navigable from its mouth, in the estuary of the Forth, up to the village of Carron Shore, and thus far vessels drawing seven or eight feet water may ascend at neap tides; but still larger vessels come up for a shorter way to Grangemouth, where this river connects by means of a tide-lock with the Forth and Clyde Canal, and is indeed the only entrance to it from the Forth. But from the Carron Iron Works, which are situated farther up on this river, there is a cut southward to that same canal at the village of Baumsford.

iver, Renfrewshire, sometimes called the White Cart, is navigable for about five miles, from the town of Paisley northwards to the Clyde near Inchinnan; but this navigation is now in a great measure superseded by the Glasgow and Paisley Canal.

The Chelmer and Blackwater Navigation extends eastwards from the basin at Chelmsford to the tideway at Collier's Reach, a distance of thirteen miles and five eighths, partly by the course of the river Chelmer, and partly by cuts, viz., first, to Burleigh Mill, ten miles and seven eighths, with a fall of fifty-nine and a half feet; thence to Heybridge, one mile and an eighth, falling seven feet; and thence by a canal of one mile and five eighths to the basin at Collier's Reach, with a fall to low-water mark of twelve feet and two thirds. From this, the length of the estuary of Blackwater to the sea opposite Sales Point is about eleven miles.

anal, see Ellesmere.

The Chesterfield Canal commences in the tideway of the Trent at Stockwith, in Nottinghamshire, near the mouth of the Idle. The general direction of its crooked course is south-west to Chesterfield, a distance of forty-six miles, having a rise of 335 feet, and fall of eighty-five feet, with sixty-five locks. Between Harthill and the village of Wales there is a tunnel of 2850 yards on the summit-level.

iver becomes navigable at Glasgow, and proceeding thence westward by Govan and Renfrew, it receives the river Cart a little below that town. From this it gradually expands into a fine estuary, which, at Port-Glasgow, becomes fully two miles wide. Along the course of the river, the distance from Gorbals Bridge in Glasgow, to the mouth of the Cart, is about seven miles; thence to Bowling Bay, where it is joined by the Forth and Clyde Canal, four and a half; thence to Dumbarton harbour, three; and thence to Port Glasgow, five. But the total length of the navigable part of this river to where it falls into the Frith of Clyde opposite Roseneath, is about twenty-five miles. Under the act 6 Geo. IV. this navigation was to be made thirteen feet deep at neap tides. The trade upon it is very extensive.

Colne River is navigable from the Hythe, near Colchester, to the sea. From the Hythe to Wivenhoe the distance is three miles and a half, and thence the river expands into an estuary extending four miles and a half farther to the sea opposite the isle of Mersea.

Conway River, Denbighshire, is navigable in the tideway from Llanrwst to its mouth at Conway harbour, a distance of thirteen miles and a half.

Coombe Hill Canal extends from this village in Gloucestershire to Fletcher's Leap on the Severn, a distance of three miles and a half, falling fifteen feet.

The Coventry Canal commences at the Trent and Mersey, or Grand Trunk Canal, on Fradley Heath, whence it goes southerly to Huddlesford, being there joined by the Wyrley and Essington Canal. It next proceeds to Fazeley, near Tamworth, where the Birmingham and Fazeley Canal locks down into it. It then crosses the Tame by Amlington, approaching the Little Anker River, running parallel to it; then by Polesworth and Hartshill it proceeds to its termination at Coventry. The whole track just mentioned amounts to thirty-seven miles and three fourths, but of this the second five miles and a half from the north end now belong to the Birmingham Canal. From Fazeley to Atherstone, about ten miles, there is a rise of ninety-six feet, by thirteen locks.

Cree River is navigable about eight miles in the tideway from Carty, near Newton-Stewart, to Creetown, in Wigton Bay.

The Crinan Canal, in Argyllshire, runs nearly south-east from Crinan, in the Sound of Jura, to Ardreshag in the frith of Loch Fine, and is about nine miles and a half long by from twelve to fifteen feet deep, with fifteen locks. From the west it rises fifty-nine feet to the summit-level, and then falls fifty-eight feet to the east. This short ship canal tends greatly to simplify and abridge the navigation in this quarter, as it cuts off about sixty miles from the long isthmus or tongue of land called Cantire, which vessels must otherwise double or go round.

The Cromford Canal, eighteen miles in length, proceeds from the head of the Nottingham Canal by Hynor Harly, Tadmoor, and Critch, to Cromford, near Matlock. In the first four miles it rises eighty feet, and the rest is level. It has several tunnels; one at Ripley is 2966 yards long.

Crouch River is navigable in the tideway from Hull bridge, in Essex, to its mouth in the sea at Foulness, a distance of sixteen miles.

The Croydon Canal commences in the Grand Surrey Canal, near Deptford, and extends nine miles and a half southward to Croydon. It rises about 150 feet, by twenty-six locks.

Darent River is navigable about four miles in the tideway from Dartfort to Longreach in the Thames.

Dart River is navigable about twelve miles and a half in the tideway from about a mile above Totness down to Start Bay in the English Channel.

The Dearne and Dove Canal commences in a side cut of the Don or Dunn River, between Swinton and Mexborough, and terminates in the aqueduct carrying the Barnaley Canal over the river Dearne. It is about nine miles and a quarter long, and rises altogether 127 feet, by eighteen locks.

Deben River, Suffolk, is navigable about nine miles and a half in the tideway from Wilford Bridge, about a mile above Woodbridge, down to the sea about four miles north of Harwich. At high water it has the appearance of a considerable estuary, and at Woodbridge and Rams- Navig. holt there are docks for ship-building and commodious wharfs.

Dec River, Cheshire, is navigable in the tideway for large vessels from Hand Bridge, at the city of Chester, by a new channel of eight miles, to where it enters the estuary of the Dee; and thence by the low-water channel to the opening into the Irish Sea off Great Helbre Island, which is a farther distance of fifteen miles and a half. At Chester this river connects with the Chester Canal.

The Derby Canal commences in the Trent, near Swarkestone, and about three furlongs to the north enters the Grand Trunk Canal, having risen twenty-six feet. From this to Derby, five miles and a quarter, it rises twelve feet, and, crossing the Derwent, proceeds three miles and a quarter by Little Chester and Breadsall, rising seventeen feet, to its termination at Little Eaton. From the east bank of the Derwent a branch extends eight miles and a half to the Erewash Canal, falling twenty-nine feet.

Derwent River, in Derbyshire, is navigable from the town of Derby, with a very tortuous course, till it falls into the Trent at Wilden Ferry, below Shardlow, where the Grand Trunk or Trent and Mersey Canal connects with that river. This navigation extends about thirteen miles.

Derwent River, in Yorkshire, is navigable from Yedingham Bridge to Barmby, in the tideway of the Ouse, about seven miles below Selby, a distance of forty-nine miles and a half, viz. from Yedingham Bridge to New Malton eleven miles and a half, thence to Howsham Hall nine and a half, thence to Stamford Bridge six and a quarter, and thence to the Ouse twenty-two.

The Donnington Wood Canal commences in the Shropshire Canal, near its junction with the Shrewsbury Canal, and runs north-east, for seven miles, to Pave Lane Wharf, near Newport.

Douglas Navigation, see Leeds and Liverpool.

The Driffield Navigation, eleven miles in length, commences at Aike Beck Mouth, in the river Hull, and ends at Great Driffield. The first five miles is in the Hull, and the remainder by a canal. The Hull and Leven Canal, of three miles, is a branch of this.

Droitwich Canal extends five miles and three quarters from Chapel Bridge, in that town, to Hawford, on the Severn, descending fifty-nine feet and a half, by eight locks. It is fed from salt springs.

The Dudley Canal proceeds from the Worcester and Birmingham Canal, near Selly Oak in Worcestershire, and passes a little east of Hales Owen, and north of Dudley, to the Old Birmingham Canal, near Tipton. From near Dudley it proceeds to the Black Delph and Stourbridge Canals. For the first ten miles and a half it is level to the Black Delph, thence two miles to Stourbridge it falls eighty-five feet by nine locks, and in three quarters of a mile to the Dudley tunnel it rises thirty-one feet by five locks. Through the 2926 yards of the tunnel it is level; thence, in one furlong, to Old Birmingham Canal, it falls thirteen feet by two locks. The main line is thirteen miles long. There are two more tunnels, one at Lapal of 3776 yards, and another at Grotsy Hill, 623 yards.

The Dun River Navigation, consisting of parts of the river Dan or Don, and short pieces of canal alternately, commences in the Ouse at Goole Bridge, and extends south-west about thirty-nine miles to Tinsley, near Sheffield, where it is joined by the Sheffield Canal. The total rise is ninety-two feet and a quarter, by sixteen locks.

Eden River has been made navigable ten miles and a half in the tideway from Carlisle Bridge, by Kirk-Andrews and Rockcliff, to Burgh Marsh Point, where it empties itself into the Solway Frith. It has been in some measure superseded by the Carlisle Canal.

The Edinburgh and Glasgow Union Canal has its western extremity at lock No.16 of the Forth and Clyde Canal, from the south-eastern bank of which it rises 110 feet, by eleven connected locks, to a height which enables it to be continued for thirty-one miles wholly on one level to its termination at Edinburgh. These locks are a little west of Falkirk, which the canal passes on the south, proceeding eastward through Prospect Hill tunnel of 696 yards in the solid rock, then over the Avon by a stupendous aqueduct bridge eighty feet above the water of that river. This is about two miles west of Linlithgow, which the canal passes close on the south, and continuing east six miles farther, turns south past the villages of Winchburgh and Broxburn, and then east again to the aqueduct bridge by which it crosses the river Almond; thence by Ratho to another aqueduct bridge at Slateford over the Water of Leith; and finally, to Port Hopetoun Basin at Edinburgh. This canal is forty feet wide at top, twenty at bottom, and five deep. The late Mr Telford recommended to continue the line of this canal from Falkirk to lock No. 20, at the eastern extremity of the Forth and Clyde summit, and to reserve the more depressed junction at No. 16 for the Grangemouth trade only. By this mode about nine fewer locks would need to be passed in the journey between Edinburgh and Glasgow; and both canals would require less water, especially as the Union Canal would then throw a large quantity of water into the summit of the Forth and Clyde Canal, which the latter now receives at too low a level to be of any use.

The Ellesmere and Chester Canal begins at Ellesmere Port in the tideway of the Mersey, about ten miles southeast of the port of Liverpool, proceeding south by Stoke, Werrin, and between Moston and Mollington Hall to Chester, where a short branch locks down into the river Dee. From this it passes east by the north wall of the city, then more southerly by Christleton and Beeston Castle, to Wardle Green, from which a branch goes to join a branch of the Grand Trunk at Middlewich. The main line proceeds a mile and a half from Wardle Green to near Hurleston, whence another branch proceeds to near Darford Hall near Nantwich, and connects with the Birmingham and Liverpool Junction Canal. From Hurleston the main line proceeds southward by Barland to Woodcot, and thence westward to near Whitechurch, where the canal enters Shropshire. Next, passing close by a detached part of Flintshire, it reaches the Cottage; and then continuing westerly by the south side of Ellesmere, to which there is a short branch, it turns more southerly to Francon Common, where the Llanymynech branch proceeds from it to the Montgomeryshire Canal. The direction of the main line is again westerly by Halston Hall, crossing the river Ceiriog by a fine aqueduct, then through Clirk Tunnel to the river Dee, which it passes by means of the famous cast-iron aqueduct bridge at Pont-y-Cysylte. (See the article Aqueduct.)

The entire length of the main line from the Mersey to the Montgomeryshire Canal is sixty-one miles, viz. to Chester, eight miles and a quarter, with a rise of forty-six feet; to Hurleston Locks, fifteen miles and three quarters, with a rise of 131 feet; to Francon Common, twenty-five miles, with a rise of 115 feet; and to the Montgomeryshire Canal, eleven miles and a half, with a fall of fifty-two feet. The branch to meet the Birmingham and Liverpool Junction Canal is two miles, and level. The branch from the Cottage to Edastaston Wharf is three miles; the branch to the town of Ellesmere is one furlong; the branch to the Rumbon Brook Railway is fully eleven miles; and that from Wardle Green to the Grand Trunk is nearly ten miles, with a fall of forty-four feet. This navigation, considering its extent, is remarkable for having been principally undertaken for agricultural purposes, the supply of towns and manufactories being a secondary consideration, though these have been greatly benefited by it. For many other particulars, see Priestley's Account of Canals. The English and Bristol Channels Ship Canal was projected principally with the view of shortening and rendering more certain and expeditious the passage of vessels trading from the Bristol Channel, the ports of Ireland, and the western ports of Britain, to the English Channel. Its length is to be forty-four miles and five eighths from its southern extremity, at Beer Roads, Seaton Bay, in the English Channel, to the northern, in Bridgewater Bay, in the Bristol Channel, which is shorter by fully 220 miles than going round the Land's End. The width is to be ninety-feet, with a depth of fifteen.

The Erewash Canal proceeds from the Cromford Canal, near Langley Bridge, to the Trent, near Sawley Ferry, being eleven miles and three quarters long, with a fall of 109 feet. The Nut-Brook Canal proceeds from the middle of this, and farther down it receives a branch of the Derby Canal, and near Sawley the Trent Canal.

The Exe River and Exeter Canal. The estuary of the Exe is navigable for eight miles, from Exeter up to the town of Topsham, and a little above this a canal proceeds from the river, running fully three miles up its west side. It is said that the first lock constructed in England was on this navigation, in 1675. But in 1829 an act was passed for making the canal enter the estuary at the Turf, two miles lower down, which will increase its length to five miles, with a depth of fifteen feet.

Forth River begins to be navigable at Stirling Bridge; but the tide reaches a little farther, to Craigforth Mill. From this downward the windings of the river are singularly intricate; its course to Alloa measuring more than three times the direct distance, which is only seven miles. On this account, although vessels of from sixty to seventy tons have water enough to Stirling, it is visited by few excepting steamers. About three miles above Alloa the Forth receives the river Devon, which is itself navigable for a short way, and very susceptible of great improvement. From this the Forth gradually expands into an estuary two miles wide opposite the mouth of the Carron, which is at the distance of thirty miles from Stirling by water. This estuary, called the Frith of Forth, continues eastward about forty-six miles farther to the Isle of May, where it may be reckoned to enter the German Sea.

The Forth and Clyde Canal commences in Grangemouth harbour, in the small river Carron, about two miles by the low-water channel, above its mouth in the estuary of the Forth. The general direction of this canal is that of west by south. It at first runs a considerable way on one level along the south side of the Carron, with which it again communicates by a cut from it at Bainsford, to that river at the Carron Iron-Works. The main line then passes to the north-west of Falkirk, and thence to Bonny Bridge, proceeding by the south side of Killyleagh, and along the south bank of the river Kelvin, and over the Logie Water by a stone aqueduct at Kirkintilloch. It then reaches Hamilton Hill about two miles from the north-west quarter of the city of Glasgow, to which there is a branch of two miles and three quarters, communicating with a branch from the Monkland Canal at Port-Dundas basin. The main line now proceeds westerly, crossing the Kelvin by a noble aqueduct, and then runs along the side of the Clyde, till it at length locks down to that fine river at Bowling Bay. The main line is thirty-five miles long, fifty-six feet wide at top, twenty-seven at bottom, and ten feet deep. In ten miles and three quarters from Grangemouth to the summit, it rises 156 feet by twenty locks. The summit-level continues about sixteen miles, and from it to the Clyde there is a descent of 156 feet by nineteen locks. Each lock is seventy-four feet long by twenty wide. At lock No. 16 from Grangemouth, this canal connects with the Edinburgh and Glasgow Union Canal.

Few canals have proved so lucrative as the Forth and Clyde. Instead of having its eastern extremity in the Carron, it was originally intended to have had it considerably farther east, or lower down the Forth, in the deeper water at Borrowstowness. This would certainly have been an immense improvement, but probably not so easily executed as some imagine; for the work was really once considerably begun, and after all abandoned, chiefly, we presume, from the difficulty of passing over the river Avon, without raising the canal a good deal for several miles along the low curse lands. The remains of a bungled aqueduct bridge for this purpose were lately to be seen on the banks of that river.

The Foss Navigation, in the north riding of Yorkshire, follows the course of the river Foss from Stillington Mill, partly in that river and partly by canal, for about twelve miles and a half, to the Ouse, at York, descending forty-seven feet and two thirds.

Foss-dike Navigation commences in the Trent, at Torksey, continuing south-east on one level for eleven miles, through a flat country, to Brayford Mere, near Lincoln High Bridge, where it is joined by the river Witham; and about five miles west of Lincoln it receives the river Till. At Torksey is a double lock, with gates pointed both ways. This canal is supposed to have been first executed by the Romans.

Gippen or Gipping River has been made navigable from near Stowmarket for sixteen miles in a south-easterly direction, to where it falls into the tideway of the Orwell, on the south side of the town of Ipswich, near Stoke Bridge. From this the estuary of the Orwell extends about twelve miles to the sea at Landguard Fort.

Glamorganshire or Cardiff Canal commences about one mile and a half below Cardiff, on the east side of the river Taff, near its entrance into Penarth harbour. It runs north-west, parallel with the Taff, by the city of Landaff, crossing the Taff by an aqueduct bridge, and it is then joined by the Aberdare Canal. Still keeping up the vale, it reaches its termination at Merthyr Tydfil; the total length being about twenty-five miles, with a rise of 611 feet.

The Glasgow, Paisley, and Ardrossan Canal, though originally intended to connect these places, and to be thirty-two miles and three quarters long, has as yet only been executed for twelve miles. It begins at Port Eglinton, near Glasgow, proceeding westerly by the north bank of the White Cart River, along which it continues till near Paisley, where it crosses that river, and then passes on the south of that town to its termination at Johnstone. It is twenty-eight feet wide at top, fourteen at bottom, four and a half deep, and all on one level. The excavation of the rest of the canal seems to be quite laid aside; but the line is to be continued to Ardrossan by a railway now in the course of being constructed.

Glastonbury Navigation begins at the confluence of the rivers Brue and Parrett, in the Bristol Channel, running along the course of the Brue to Highbridge, and is to be continued by a canal, partly in that river, to the west side of the town of Glastonbury, in all fourteen miles and a quarter.

Glenkens Canal, on the Solway, though described in various books for the last thirty-five years, has never yet been executed.

The Gloucester and Berkeley Ship Canal begins in the Severn, at Sharpness Point, about three miles north of the town of Berkeley, proceeding by Slimbridge and Saul, and, crossing the Stroud Canal on the same level, it passes Wheatenhurst, Hardwick Court, and Hempstead House, and reaches the city of Gloucester, where it terminates in a spacious basin, out of which there is a lock into the Severn. The distance between Sharpness and Gloucester by the Severn is twenty-eight miles, whilst by the canal it is only sixteen and a half, and avoids a difficult and often dangerous navigation. The width of this canal is seventy feet, depth eighteen, and it is level throughout.

The Grand Junction Canal proceeds from the Thames at Brentford, across the Brent rivulet, to the valley of the Colne, which it continues to follow past Uskbridge, Rickmansworth, Walford, King's Langley, Two-Waters, Berkhamstead, to the summit-level at Cowroast; being thirty-five miles and three eighths, with a rise of 395 feet, and through an almost continued series of mill pools. The summit-level extends only three miles and three fourths to Tring, and is chiefly in deep cutting. From Tring the canal continues by Marsworth, near to Leighton Buzzard and Fenny Stratford, to the Ouse at Wolverton, near Stony Stratford, a distance of twenty-five miles and a quarter, with a descent of 192 feet. Here it crosses the Ouse on a small aqueduct, and an embankment half a mile long. Then running along the western side of, and having crossed the Five Rivers, the canal arrives at Stoke Bruerne, being a distance of six miles and a half, with a rise of 112 feet. It next goes through Blisworth tunnel, of 3080 yards, proceeding by Western Beck to the southern extremity of Whilton parish, being thirteen miles and a half, on one level. In three quarters of a mile from this to Whilton Mill it rises sixty feet, and then continues level for four miles and a quarter, to the farther extremity of Braunston tunnel, of 2045 yards. It is seven eighths of a mile, with a fall of thirty-seven feet, from this tunnel to the junction with the Oxford Canal. The total length of the main line of the Grand Junction between the limits now mentioned is ninety miles and a quarter. Its average width is forty-three feet, and depth from four and a half to five feet. The locks are eighty-two feet long by fourteen and a half wide. The Paddington branch, of thirteen miles and a half, is of the same dimensions. It connects with the main line about midway between Uxbridge and Brentford, and again with the Regent's Canal at Paddington. From Tring a level branch of six miles and three quarters reaches near Wendover; and, a little north of Tring, a branch of six miles goes to Alyesbury, falling ninety-five feet. From the embankment over the Ouse, a branch of nine miles and a half proceeds to the town of Buckingham; and another of nine miles from Gayton, by Old Stratford, to the Nen, near Northampton. By means of the Grand Junction a communication has been opened between London and the great manufacturing districts in the interior of the kingdom.

The Grand Surrey Canal commences at Wilkinson's Gun Wharf, on the south bank of the Thames, about a quarter of a mile east of the Thames Tunnel, and passing 1200 yards through the docks of this navigation, its course is southward, approaching at Bridge Place within 250 yards of the King's Dock Yard at Deptford, near to where it is joined by the Croydon Canal. It then turns west by Peckham New Town to the north side of Adlington Square, where it terminates. It is four miles and two chains in length.

Grand Trunk, see Trent and Mersey.

The Grand Union Canal unites with the Leicester Union Canal near Foxton, about four miles from Market Harborough, to which there is a branch. Its course is southerly, passing through a tunnel of 1166 yards at Bosworth, between Lutterworth and Northampton, and thence by Elkington and Guildsborough to Crick, at which there is a tunnel of 1524 yards. Then leaving Watford on the east, it continues to its termination in the Grand Junction Canal at Long Buckby. The entire length is about forty-five miles, with an ascent of seventy-six feet by ten locks, and a fall of fifty-four feet by seven locks.

Grantham Canal commences at the town of that name in Lincolnshire, passing Harlaxton, Woolsthorp Point, Stainwith Close, Cropwell Butler, to its termination in the river Trent, nearly opposite the mouth of the Nottingham Canal. The length is about thirty-three miles, with a fall of a hundred and forty-seven feet and a half. A branch of three miles and a half goes to the town of Bingham.

Gresley Canal forms a short connecting portion between or in the line of the Newcastle-under-Line Canal and the Newcastle-under-Line Junction Canal, the principal purposes of which are for conveying coals from the Apdale and Partridge Collieries on the west, and the Caldon line from the east.

The Hartlepool Ship Canal connects the Hartlepool harbour with the sea. It is 800 yards long, and nineteen feet deep, being cut through the solid rock.

Hereford and Gloucester Canal commences in the Severn opposite Gloucester, crosses Alney Ise and another branch of the Severn to Lassington, and terminates at Bysters's Gate in Hereford. In eighteen miles from the Severn to Ledbury it rises 195 feet, and then continues on the summit-level eight and a half miles to Monkhide, from which it descends thirty feet in three miles to Withington March, and thence to Hereford, six miles, it is level. The total length is thirty-five miles and a half, with three tunnels of 2192, 1320, and 440 yards respectively.

Hertford Union Canal is a cut of one mile in length, to connect the Hackney Cut of the River Lea Navigation at White-Post Bridge, near Temple Mills, with the Regent's Canal at Old Ford Lock, Bethnal Green. It is also called the Lea Union and Sir George Duckett's Canal.

The Horncastle Navigation commences in the Old Witham River, near Tattershall, Lincolnshire, and partly occupying the bed of what was formerly the Tattershall Canal, proceeds to Horncastle by the course of the Bain River. It is about eleven miles long, and very little elevated above the sea.

Huddersfield Canal commences on the southern side of that town, running south-west by Slaithwaite, nearly parallel with a branch of the Colne, for seven miles and a half, which river it crosses three times by aqueducts; and, ascending 436 feet by forty-two locks, it attains, near Marsden, the highest summit-level in the island, being 656 feet above the sea, but only four miles long. This is principally occupied by the Standedge tunnel, of 5451 yards, which is upwards of three miles, being the largest in Britain, from which the canal emerges into the vale of Diggie in Saddleworth, to near Wrigley Mill. It then glides along the valley alternately on the north and south sides of the River Tame, past Dobcross, Scout, and Stayley Bridge, to its junction with the Manchester, Ashton, and Oldham Canal, near Duckinfield Bridge; having passed a farther distance of eight miles and a quarter, with a descent of 3844 feet by thirty-three locks. There is a tunnel at Scout of 240 yards, and another at Ashton of 198 yards. This canal forms part of the shortest water communication between the east and west coasts.

Hull River, see Driffield.

Itchin Navigation follows the course of the river Itchin from Blackbridge, near the city of Winchester, to the tide-way at Northam, near the town of Southampton, a distance of fourteen miles.

Ivel River, which empties itself into the Ouse at Tempsford in Bedfordshire, has been made navigable for five miles and three fourths, up to Biggleswade; and it has long been proposed to extend it five miles and a quarter further, up to Shefford.

Ivelchester and Langport Canal, in Somersetshire, is nearly seven miles long, running eastward from its commencement in the river Parrett, below the town of Langport, to Ivelchester or Ilchester.

Kennet and Avon Canal commences at the head of the navigable part of the river Kennet, at Newbury in Berk- shire, and passes up the valley of that river by Hungerford and Great Bedwin to Crofton, a distance of sixteen miles and a half, rising 210 feet by thirty-one locks. From this the summit-level continues two miles and a half, through a tunnel of 510 yards, to Brimsalde. In one mile farther there is a descent of thirty-three feet by four locks to Wootton-Rivers, from which the canal continues fifteen miles along the vale of Pewsey, on one level, to Devizes; and in the next two miles and a half to Foxhanger it falls 239 feet by twenty-nine locks. Other four miles and a half, descending fifty-six feet by seven locks, bring it to Semington, where it is joined by the Wilts and Berks Canal. From this it passes five miles and a half to Bradford, and there descends ten feet by one lock into the vale of the Avon, along which it continues nine miles on one level to Sidney Gardens, Bath; and in about a mile farther it descends sixty-six feet and a half by seven locks into the Avon, near the Old Bridge. From this the Avon itself is navigable downwards by Bristol into the Severn. The entire length of the canal is fifty-seven miles; the breadth is forty-four feet at top, twenty-four at bottom; and the depth is from five to six feet. Few canals afford more specimens of deep cutting, aqueducts, and tunnels, than the Kennet and Avon. It completes a circuit of navigable canals, which, traversing the northern, midland, and southern counties of England, connect its four largest rivers, the Trent, the Mersey, the Severn, and the Thames. Thus, by uniting the rivers Kennet and Avon, the former of which runs into the Thames at Reading, and the latter into the Severn a few miles below Bristol, this canal becomes the central line of communication between the Irish and the German Seas.

Kennet River has been made navigable from where it falls into the Thames, about a mile and a half below Reading, up to its junction with the Kennet and Avon Canal at Newbury, in Berkshire, a distance of twenty miles. It ascends 126 feet, by twenty locks.

Kensington Canal, 3000 yards long, consists of Counters Creek, greatly enlarged and improved, its mouth being in the Thames, near Counters Bridge, on the road from London to Hammersmith.

Kelty Canal, see Shropshire.

Kingston Canal, see Lecminister.

Lancaster Canal commences at Bark Hill, near Wigan, passing Chorley to Clayton Green, near the south bank of the river Ribble, a distance of thirteen miles and a half, which is level. From this across the valley of the Ribble to the top of its north bank the distance is four miles and a quarter, with a depression of 222 feet, which is passed by a railway and inclined plane on each side of the valley. From this railroad, past Garstang and Lancaster to Tewitfield, near Barwick, a distance of forty-two miles, the line of the canal is on one level, and is commonly called the Lancaster Level. In the next thirteen miles, to its termination at Kirkby-Kendal, it rises sixty-six feet. The general direction of this canal is north, and the entire length about seventy-three miles. It has a magnificent aqueduct over the river Lune, near Lancaster, being fifty-one feet above the river, and having five arches of seventy feet span each.

The Lark or Burn River, in Suffolk and Cambridgeshire, is navigable for fourteen miles, from Long Common, a little below Mildenhall Mill, to Eastgate Bridge, in Bury St Edmunds. Being connected with the Ouse, near Littleport, it is a very useful navigation.

Lea River Navigation commences at the town of Hertford, proceeding easterly by Ware to its junction with the Stort River Navigation, near Hoddesden, from which it veers south to Waltham Abbey, and preserves the same direction to Oil Mill, where, again bending south-east by Wanstead and Aldersbrook, it arrives at Temole Mills. A little above this it is connected with the Regent's Canal by a cut of one mile, called the Hertford or Lea Union Canal. From Temple Mills the Lea proceeds to its descent into the Thames at Bow Creek. At Bromley there is a cut of one mile and a half, falling seventeen feet and a half into the Thames at Limehouse. The track of the Lea from the Hertford to the Thames is about twenty-six miles; and connected with it is the canal called the New River, which supplies London with water.

The Leeds and Liverpool Canal commences at Leeds Bridge, where it unites with the Aire and Calder Navigation, and terminates at North Lady's Walk, Liverpool, a distance of 127½ miles. In the course of forty-one miles from Leeds to the summit-level, near Greenberfield, the total rise is 411 feet; from the summit near Colne, to the basin at Liverpool, there is a fall of 433 feet; and from the basin to low water in the Mersey the fall is fifty-six feet. It is to be observed, that of this line of navigation eleven miles belong to the Lancaster Canal; that is, from Copshurst, or Johnson's Hillock, to Kirklees. The great tunnel of Foulridge is 1640 yards long, eighteen feet high, and seventeen wide. At Bingley, a connected series of five locks effect the enormous lift of eighty-eight feet and two thirds, which must often occasion a great waste of water, unless recourse be had to some additional artifice. This canal was forty-six years in hand, being begun in 1770, and finished in 1816.

The Leicester Navigation commences at the basin of the Loughborough Canal, and proceeds three miles to the separation of the Melton-Mowbray Navigation. (See Wreak and Eye Navigation.) From this the distance is eleven miles, with a rise of forty-five, to its termination in the Leicestershire and Northamptonshire Union Canal.

The Leicestershire and Northamptonshire Union Canal, commencing at the junction with the Leicester Navigation, proceeds partly in the bed of the river Soar, and partly by an artificial course, to the Grand Union Canal at Gumley Hall, a distance of seventeen miles, rising 160 feet. From the last place a branch of four miles goes to Market Harborough. There is a tunnel half a mile long at Saddington.

The Lecminister Canal commences at Kington, 505½ feet above the sea, where it meets the Kington Railway; thence observing an easterly direction, it passes to the aqueduct over the Lugg at Kingsland, and then bends south to near Lecminister. From this town it runs north for a considerable distance past Berrington House, then turns east with many windings past Tenbury to the aqueduct over the Rea, and the tunnel at Sousant, which is 1250 yards long. From the latter, which is 2644 feet above the sea, the canal runs eastward to its termination at Stourport, where it unites with the Severn and the Stafford and Worcester Canal, having described a track of forty-six miles. From Kington to Staunton Park it is level for four miles, then falls 152 feet in two miles and a half to Milton, thirty-seven feet in three miles and a half to Kingsland aqueduct, and sixty-four feet in four miles and a half to Lecminister. In the next mile and a half it rises eighteen feet, and in five miles and a half farther to Wiston it is level; thence to Letwich Brook it falls thirty-six feet in four miles and a half. The next seven miles to Ren are level, then is a rise of thirty-five feet in one mile to Sousant tunnel, then nine level miles to Great Pensax tunnel of 3850 yards. But in the last three miles to the Stafford and Worcester Canal there is a fall of 207 feet; the total fall being 496 feet, and the rise forty-eight.

The Leven Canal is a cut of three miles from the village of Leven to the Driffield or Hull River Navigation.

Lewes, see Ouse River, Sussex.

The Liskeard and Looe Canal commences at Tarras Pill, and runs northward to Moorswater, in the parish of Liskeard, in Cornwall. It is five miles and seven eighths long, rising 156 feet by twenty-five locks. It has a branch of one mile to Sand Place.

Louth Canal runs from that town northwards by Lea- therhill Mead and North Cockering to Titney, in the mouth of the Humber, a distance of fourteen miles, falling fifty- six feet and a half.

The Loyne or Lune River is navigable about seven miles in the tideway from Lancaster Bridge to its mouth in Lan- caster Bay.

Lynn River, see Narr.

Macclesfield Canal commences near the north end of the summit-level of the Peak Forest Canal, and passes through a very undulating part of Cheshire to the road from Buxton to Congleton, where it locks down to its low- est level; then crossing the Dane, it runs south-west to its termination in the summit-level of the Trent and Mer- sey Canal, a distance of twenty-nine miles and a half, with a total fall of 113½ feet. This, when executed, will shorten the communication between London and Manchester about thirteen miles.

Manchester, see Ashton.

The Manchester, Bolton, and Bury Canal ascends sixty- eight feet and one third, by six locks, from the Irwell to the basin in Salford; thence for four miles running parallel to the Irwell it is level, but in the next three miles it rises 121 feet by twelve locks. The remaining four miles to Bolton are level, and so is a branch of four miles to Bury.

Market Weighton Canal commences at New River Head, near Market Weighton, and runs almost directly south for eleven miles to its termination, with a sea-lock at Foss-dike Clough, in the Humber. Near the upper end are three locks.

The Medway River begins to be navigable for barges at Penhurst Bridge, about six miles above Tunbridge, and about forty-five miles by the crooked course of the river, from its mouth in the Thames at Sheerness; but some de- duction should be made for several bends being now cut off. The tide formerly reached up to Maidstone, but has been obstructed by locks and weirs. Below Rochester Bridge this river is in many places of great width, and so deep as to float the largest vessels at low water, thus affording a safe and extensive harbour for Chatham dock-yard. A little below Rochester Bridge it is joined by the Thames and Medway Canal, and near its mouth by the East Swale or tide passage round the south side of the Isle of Sheppey.

The Mersey and Irwell Navigation commences in the estuary of the Mersey at Runcorn Gap, and terminates at the bridge between Manchester and Salford. It con- sists in these rivers improved by locks, weirs, and exten- sive side-cuts, so as to be conveniently navigable over a distance which by the course of the rivers exceeds fifty miles. The various canals connected with the Mersey and Irwell render this an undertaking of great utility.

The Monkland Canal begins at Old Monkland Colliery, and runs nearly direct west for twelve miles to Port Dun- das at Glasgow, where it communicates with a branch of the Forth and Clyde Canal, to which it acts as a feeder. In its course it receives the Monkland and Kirkintilloch, Garnkirk and Glasgow, and Airdrie Railways. At Sheep- ford it falls twenty-three feet by two locks, and at Black- hill ninety-six feet by twelve locks. It is thirty-four feet wide at top, twenty-four at bottom, and four and a half deep.

Monmouthshire Canal commences in the Usk River, a little below Newport, close to the termination of the Rum- ney and Sirhowey Railways. Passing northward, this ca- nal extends by Pontypool to Pontnewynydd, a distance of fully seventeen miles and three quarters. Near the latter place it connects with the Abergavenny and Brecknock

In the last twelve miles it rises 447 feet; and opposite Malpas, a branch of eleven miles, rising 338 feet, goes to Crumlin Bridge. There are various extensive railway branches from this canal.

Montgomeryshire Canal commences at Porthywaen lime- works, where it joins a branch of the Ellesmere Canal; and having passed the village of Llany-mynach, and cross- ed the Vernview River, it joins another branch of the El- lesmere Canal. Next running to Gwern-felu, where a branch to Gullsfield turns off, it proceeds to Welchpool; after this it runs parallel to the Severn, which it at length joins on the east side of Newton. It is about twenty-sev- en miles long, running in a south-west direction, with a lockage of 225 feet.

Narr or Lynn River is navigable from the Ouse at King's Lynn to Castle Acre in Norfolk, a distance of about fif- teen miles.

Neath Canal commences in the tideway of the Neath, at Giant's-grave-pill, in Briton's Ferry, and running north- west, terminates in the Aberdare Railway branch at Aber- nant, a distance of fourteen miles. It has various other railway branches to the neighbouring collieries, &c.

Nen or Nyne River is navigable from the sea below Wisbeach, through the Fens to Peterborough, and from that by the natural channel, improved by cuts and locks, to Northampton, which forms a course of about ninety- nine miles. Beginning in the Wash at Peter's Point, and passing up nine miles to Wisbeach, the navigation may ei- ther be continued thence to Outwell by the course of the river, or by the still shorter track of the Wisbeach Canal, which also forms a communication between these places. But the navigation likewise proceeds from both places by two or three embanked courses through the Fens to Pe- terborough, a farther distance of forty miles; and thence by the original channel, greatly improved by cuts, weirs, and locks, for fifty miles more, up to the town of North- ampton, to which a canal branch descends 112 feet from the Grand Junction Canal. Near Salter's Load the Nen communicates with the Ouse by means of Well Creek; and a still shorter navigation has been formed from Wis- beach to Lynn, through the Wisbeach Canal. The above may give some idea of the principal lines of navigation belonging to this river; but since most of the rivers and navigable drains in the fens are embanked on both sides, and since they are almost still water too, this occasions such a number of navigable branches intersecting and crossing in all directions, that a description of them would greatly exceed our limits.

The Newcastle-under-Line Canal extends about three miles westward, from the Trent and Mersey Canal at Stoke- upon-Trent to Newcastle, in the Newcastle-under-Line Junction Canal, which again continues the line north-west for eight miles farther (including in its middle the five miles of Gresley's Canal) to Partridge-Nest and Bignell- End Collieries.

The Newport Pagnell Canal is a branch of a mile and a quarter from that town to the Grand Junction Canal at Linford, with a rise of fifty feet by seven locks.

Nith or Nidd River Navigation commences in the Sol- way Frith, and extends nearly north for about nine miles in the tideway between the counties of Dumfries and Kirkcudbright, to Dumfries Bridge; but it stands much in need of improvement.

North Walsham and Dilham Canal commences at Way- ford Bridge, in the parish of Dilham, Norfolk, in the river Ant, and runs north-west by North Walsham and Whit- ton Park, to its termination at Antingham, a distance of seven miles.

North Wilts Canal, see Wilts and Berks.

The Norwich and Lowestoft Navigation, commencing in the Wensum or Yare River at Norwich, follows partly the course of that river, and those of the Yare and Wensum, and proceeds partly through the Lake Lothing, and by cuts to Lowestoft, a distance of thirty miles. It traverses so flat a country, that a tide-lock only is necessary, which admits vessels eighty-four feet long, twenty-one wide, and drawing ten feet of water.

Nottingham Canal commences in the Trent, from which it has a winding course for about fifteen miles, with a rise of 108 feet to the junction of the Erewash and Cromford Canals at Langley Bridge.

Nuthbrook or Shipley Canal is a branch extending four miles and a half, from the Erewash Canal, near Trowen, to the Shipley Collieries.

The Oakham Canal extends from that town to Melton-Mowbray on the Leicester and Melton-Mowbray Navigation; a distance of fifteen miles, falling 126 feet.

Ouse River, Sussex, navigable naturally nine miles in the tideway up the Lewes, has, by artificial means, been rendered navigable for twenty-two miles farther, up to Hammer Bridge.

Ouse River, Yorkshire, is navigable for vessels of 150 or 160 tons from where it receives the Trent, up to the junction of the Aire and Calder Navigation at Armyn, a distance of fifteen miles, and for smaller masted vessels twenty-five miles farther to the city of York. This river, notwithstanding its limited trade above that city, has such an immense traffic in the lower part, by reason of the numerous rivers and canals communicating with the manufacturing and mining districts, that it undoubtedly ranks the second river in the kingdom in importance and utility; whilst, by its union with the Humber, merchandise is exported to and imported from all parts of the globe.

Ouse River Navigation (Bedford Level) commences in the estuary of the Wash, below the town of Lynn, and proceeding thence by a cut of two miles and three quarters, called the Earl Brink, to Salter's Load and Denver's Sluice, it is thus far, which is about seventeen miles above Lynn, an open embanked navigation. From this upwards the natural river continues navigable still by an embanked crooked course through the Fens to Ely and Hermitage Sluice near Erith, and thence onward to Bedford, altogether about eighty-four miles from the sea. From Lynn the Narr or Lynn has been made navigable fifteen miles to Castle Acre in Norfolk; and from Salter's Load the Well Creek extends to the Nen and Wisbeach Navigation. Near Denver's Sluice the Ouse receives the river Stoke, also the Old and New Bedford Rivers, which are two parallel straight cuts of twenty-one miles, joining the Ouse again at Hermitage Sluice. From this last place a navigable cut of twelve miles conveys water from the Ouse to the Nen at Benwick. At Brandon Creek Bridge the Ouse receives the Little Ouse, which is navigable for twenty-two miles and a half south-east by Downham and Santon to Thetford; and at Prickwillow it receives the Lark, navigable to Bury St Edmund's. Near Barkway the Soham Lode, navigable for four miles to Soham, falls into the Ouse. At Harrimere it receives the Grant or Cam, navigable to Cambridge, and at Tempsford the Ivel. Almost the whole of the rivers and large drains connected with the Ouse are embanked and nearly level. Many others of them are navigable for short distances besides those we have noticed, but they are chiefly used for drainage.

The Oxford Canal commences in the Coventry Canal at Longford, proceeding thence twenty-six miles and a half on one level across the upper part of the valley of the Avon to near Hill Morton, where it rises nineteen feet by three locks. About eight miles farther on it is joined by the Grand Junction Canal; and in eight miles and three quarters more, at Napton, by the Warwick and Napton Canal. Thus far the course is very crooked. In the next two miles it rises fifty-five feet by nine locks to the summit-level, on which it continues ten miles and three quarters (passing a tunnel of 1188 yards) to Claydon. From this the canal descends into the valley of the Charwell, proceeding seven miles and a quarter to Bambury, with a fall of seventy-seven feet by twelve locks. Following the Charwell, and crossing it near Hampton Gay, it passes to its termination in the Thames at Badcock's Garden on the west of the city of Oxford. The total length is about ninety-one miles; and in the last twenty-seven miles and a half from Bambury it falls 118 feet, by eighteen locks. It is twenty-eight feet wide at top, sixteen at bottom, and four and a half deep; but, to act partly as a reservoir, the summit-level is six feet deep. For various improvements and alterations on this navigation, we beg to refer to Priestley's Account of Canals, &c.

The Peak Forest Canal commences at Dukkenfield, in the Manchester, Ashton-under-Lyne, and Oldham Canal, and passes south-east fifteen miles to Bugsworth, from which the line is continued seven miles by a railway to Limestone Rock, Peak Forest.

Penclawdd Canal extends eastward from the river Burry at Penclawdd, in Glamorganshire, for three miles and three fifths, to Kingsbridge; and, though short, it is said to be of great utility.

Pocklington Canal, Yorkshire, extends from East Cowling, on the Derwent, to Street Bridge, Pocklington, a distance of eight miles and a half.

The Portsmouth and Arundel Canal commences in the tideway in the river Arun, at the village of Ford, three miles from the sea, at Arundel harbour, and proceeds westward close by Yapton, Barnham, and Merston, to half a mile from North Mundham, where the Chichester branch takes off. From this it passes by Donnington to Chichester harbour, where the principal line, which is almost twelve miles long from the Arun, terminates. The bed of the Arun is fifteen feet below high water spring tides; and there is a lock of five feet, above high-water mark, on the bank of the river. A little farther on is another lock of seven feet lift, from which the canal continues on the same level for ten miles five furlongs, to two locks, equal respectively to the two just mentioned, and similarly situated in respect of the other termination in the tideway. This canal is thirty-three feet wide at top, nineteen and a half at bottom, and four and a half deep. Both it and the Chichester branch, of a mile and a quarter, are fed by water raised by a steam-engine. The channel from the extremity of the main line of canal in Chichester harbour, round Thorney Island and Hayling Island, by Thorney and Langstone Wadeways, and Langstone harbour, to the end of the Portsea Canal, is thirteen miles and an eighth. The canal from Eastney Lake is two miles and three eighths long; there are two locks at the east end, and a basin at the termination at Portsea. This part is five feet deep, and is fed by an engine. From the end of the main line in Chichester Harbour to the canal at Cosham, the distance is fifteen miles and a quarter; and the length of the canal to Porchester Lake in Portsmouth harbour is one mile and a quarter. This branch is seven feet deep, with a sea-lock of ten feet lift at each end. These important undertakings, from their connections with so many other navigations, will tend to open a ready inland communication between this quarter and almost every part of the kingdom, and may become serviceable for conveying military stores from London to Portsmouth in time of war.

Ramsden's (Sir John) Canal, is a short connecting link of three miles and three quarters, between the Huddersfield Canal at the King's Mill near Huddersfield, and the Calder and Hebble Navigation near Cooper's Bridge. It descends fifty-seven feet and a half, by nine locks.

Regent's Canal commences in the Paddington branch of the Grand Junction Canal, near the Harrow Road, and, proceeding in a north-east direction, passes through a short tunnel under the Edgware Road, and thence runs parallel to Primrose Hill Road, till, having passed on the north of the Zoological Gardens, a branch of half a mile runs south-east to a basin at Cumberland Market. The main line preserves nearly its first direction, till, crossing the Paneras Vale Road, on the north of Camden Town, it turns more eastward; then locking down, it crosses Camden Road and the King's Road, and turns south-east across Maiden Lane, next to Horsfall's Basin, a quarter of a mile beyond which it enters the tunnel under Islington, 900 yards long, but which, most unfortunately, to save a trifle of expense, has no room for a towing-path. It next crosses the New River to Frog Lane, on the east of which is a lock, and also a branch called the basin, passing under the City Road. The main line continues eastward to Bridport Place, and, running parallel with Felton Street, it leaves a second basin on its north bank, and a little farther on a third basin on its south bank. From this it proceeds across Cambridge Heath Road, and then, bending greatly south, crosses Mile End Road, passes to Stepney Lane, crosses the Commercial Road, and finally arrives at the basin at Limehouse, by which it locks into the Thames, being a total distance of eight miles and a half, descending ninety feet by twelve locks besides the tide-lock.

At Globe Town, a cut of one mile, running north-east, connects this canal with the River Lea Navigation. It is named the Hertford Union Canal, and sometimes the Lea Union.

Ribble River, Lancashire, has been rendered navigable for eleven miles westward from Penwortham Bridge, near Preston, to its mouth in the Irish Sea.

Rochdale Canal commences in the Bridgewater Canal at Castlefield, Manchester, and about a mile from this is joined by the Manchester, Ashton-under-Line, and Oldham Canal. It then passes the town of Rochdale, and along the north border of the high ground called Blackstone Edge, to its termination in the Calder Navigation at Sowerby Bridge Wharf, a distance of thirty-one miles and a half. The rise from Knott Mill, Manchester, to the summit, is 533½ feet, and the fall from this to Sowerby Bridge is 353½. This canal is one of the main links in the chain of inland navigation between the east and west seas.

The Rother River Navigation commences at Lower Platt, near Midhurst, Sussex, and passes by Cowley Park to Amberham, and by Petworth and Burton to a little beyond Little Fittleworth, from which a cut passes to the river Arun, near Stopham Bridge, where the navigation terminates, the total length being eleven miles.

The Royal Military Canal commences in the tideway at Shorncliff in Kent, proceeding west to Hythe, and, gradually bending southward, passes on the south of Lympne and Appledore to the junction with the long proposed Weald of Kent Canal. From this it proceeds south to the river Rother, in the bed of which it continues past Rye to Winchelsea, where that river verges south-east, whilst the canal continues due south to Cliff End, and there terminates. The total length is about thirty miles, the width at top is from sixty-two to seventy-two feet, and at bottom from thirty to thirty-six, and the depth is nine feet. The locks are seventy-two feet long and sixteen wide; they are only required for the tide, and the fluctuations of the Rother.

St Columb Canal is a cut of six miles, from Maugan Porth to Lower St Columb Porth, in the county of Cornwall.

The Salisbury and Southampton Canal commences in the Itchin River at Norham, near Southampton, and runs along the north-east shore of Southampton Water to Redbridge, from which the line of navigation is continued north in the Andover Canal. From the latter, at Mitchelmersh, a branch was dug westward to Salisbury, but was abandoned because it would not hold in the water. This had not, it would seem, been thought worth a lining of clay, which, if properly executed, would make any canal hold in.

Sankey Brook Navigation, the first executed in England, originally commenced at Fidler's Ferry, at the mouth of Sankey Brook, from which it at first runs north, gradually bending west, and latterly turns south to St Helens, where it terminates. The length is about twelve miles, rising seventy-eight feet by ten locks; width forty-eight feet at top, depth five and a half. In 1830 an act was obtained for extending this navigation three miles and a quarter, from a little above Fidler's Ferry to Widness Wharf, West Bank, near Runcorn Gap.

The Severn River is navigable for 178 miles, with a descent of 225 feet, from Welshpool, through the counties of Montgomery, Salop, Worcester, and Gloucester, till it enters the Bristol Channel. Its navigable connections are the Montgomeryshire Canal at Newtown; the Shrewsbury Canal at Shrewsbury; the Shropshire Canal at the Hay; the Staffordshire and Worcestershire Canal, and the Leominster Canal, at Stourport; the Droitwich Canal at Hawford; the Birmingham and Worcester Canal at Diglis, below Worcester; the river Avon at Tewkesbury; the Coombe Hill Canal at Fletcher's Leap; the Hereford and Gloucester Canal at Gloucester; the Gloucester and Berkeley Canal, both at Gloucester and at Sharpness Point; the Stroud Canal at Framilode; the Lydney Canal below Lydney; the river Wye at Beachley; the Bristol River Avon at Morgan's Pill; and the Monmouthshire Canal at Newport.

Sheffield Canal connects that town with the river Don Navigation in the township of Tinsley. It is little more than four miles long, with a fall of seventy feet by eleven locks.

The Shrewsbury Canal commences at Rockwardine Wood, in the north extremity of the Shropshire Canal. The first mile is level. At Woombridge it descends seventy-five feet by an inclined plane; and in the next four and three quarters miles to Langdon is a farther fall of seventy-nine feet by locks. It then crosses the river Tern by the first iron aqueduct used in a navigable canal, and, proceeding by Roddington, it passes a tunnel of 970 yards, and at length runs along the bank of the Severn to its termination at Shrewsbury. The total length is about seventeen miles and a half.

Shropshire Canal commences at the Donnington Wood Canal, and passing Rockwardine Wood and Madeley, proceeds to its termination in the Severn at Conifort, two miles below Coalbrook Dale. The length is seven miles and a half. It has a rise of 120 feet, and two falls of 126 and 207 feet, all of them by inclined planes.

Seaford Navigation extends from Chapel Hill, on the Old Witham River, to the Castle Causeway near Skelton. It is about thirteen miles and a half long, thirty feet wide at top, eighteen at bottom, and five feet deep. The greater part of its course is embanked through the fens.

Soar River Navigation consists of the river Soar, made navigable for seven miles up from the Trent, and of a cut of one mile and a half, which continues it to Loughborough, where it connects with the Leicester Navigation.

Somersetshire Coal Canal commences at the Kennet and Avon Canal at Limpley Stoke, and terminates at Paulton; a distance of ten miles. It is connected with various collieries by railways.

Staffordshire and Worcestershire Canal commences in the Severn at Stourport, and proceeds northerly by Millton, Kidderminster, Tittenhall, Penkridge, and Baswich, to its termination in the Trent and Mersey Canal near Haywood, Staffordshire. The total length is forty-six miles. and a half. In the first twelve miles and a quarter from Stourport, to where it is joined by the Stourbridge Canal, it rises $127\frac{1}{2}$ feet by thirteen locks; in the next eleven miles it rises $166\frac{1}{2}$ feet by eighteen locks. The next ten miles, in which it is joined by the Old Birmingham Canal, are level; and in the remainder it falls $100\frac{1}{2}$ feet by thirteen locks. This canal is thirty feet wide at top, and five deep. The locks are seventy-four feet long, and seven feet wide, but had originally only four feet water on the sills.

Stainforth and Keadby Canal begins in the river Don, near Stainforth, Yorkshire, and passes eastward fifteen miles to the Trent at Keadby, Lincolnshire, where it has a tide-lock. There is only another lock near Thorne, of five feet lift, the tract is so flat.

Stort River has been made navigable for ten miles in Hertfordshire and Essex, from the New Bridge, Bishop-Stortford, to the river Lea at Rye near Hoddesden.

Stourbridge Canal extends about five miles from the Stafford and Worcester Canal at Stewponey, near Stourton, to the Dudley Canal at Black-Delph, from which a branch of one mile goes to Stourbridge, and another of two miles to Pensnett Chase Reservoir. It rises $191\frac{1}{2}$ feet by twenty locks.

Stour River, between Suffolk and Essex, has been rendered navigable for nineteen miles from Sudbury to Manningtree; thence to Harwich it is a wide estuary.

Stratford-upon-Avon Canal commences at King's Norton, about six miles from Birmingham, and proceeds south-eastward by Lapworth and Preston Mill to Stratford, a distance of twenty-three miles and a half, descending 309 feet. From near Hockley, a branch of two miles and a half goes to Tumworth quarries; from Lapworth another of one mile and three quarters to the Warwick and Birmingham Canal; from Wilmote another of four miles to Temple-Grafton Limeworks; and from this branch a cut of one mile to Aston Cantlow.

Stroudwater Navigation commences at Framilode, running eastward across the Gloucester and Berkeley Canal, and the Stroudwater, to Wallbridge, near Stroud, in the Thames and Severn Canal, a distance of eight miles, rising $102\frac{1}{2}$ feet.

Swale River, see Ouse.

Swansea Canal commences in Swansea harbour, and running north-eastward by Landoor, and across the small river Twrch, terminates at Pen Tawe, a distance of seventeen miles, rising 373 feet.

Tamar Manure Navigation. The river Tamar has been made navigable from Morwellham Quay (where Tavistock Canal begins) up to Boat Pool, whence a canal has been continued north-west for about twenty-two miles to Tamerton Bridge. From near Poulson Bridge a branch goes off to Launceston.

Tavistock Canal extends from the tideway in the Tamar four and a half miles north-east to Tavistock, with a rise of 237 feet. From Crebar a branch of two miles goes to the slate quarries at Millhill Bridge, rising nineteen feet and a half.

Tay River is navigable from the city of Perth, gradually widening downwards by Dundee to the German Sea, a distance of twenty-eight miles, through which the tide flows; but it only admits of large vessels reaching Perth at stream tides. It was formerly much obstructed by floods at one season, and shallows at another; but in 1830 an act was obtained for its improvement.

The Tees Navigation commences in that river at Stockton, and proceeds chiefly by an artificial course to Portrack, and thence by the estuary of the Tees Mouth to the German Sea; the total distance is about twelve miles, and level in the tideway.

Thames River having a separate article devoted to it, we shall only here treat very briefly of its navigation and navigable connections. The principal branch of this noble river, under the name of the Isis, and greatly improved by artificial means, begins to be navigable at Lechlade, about $146\frac{1}{2}$ miles above London Bridge by the course of the river, and where the Thames and Severn Canal locks into it. At Oxford it receives the Oxford Canal; at Abingdon, the Wilts and Berks Canal; near Dorchester, its other branch the Thame; at Caversham Bridge, near Reading, the Kennet Navigation; near Woburn Park and Ham, the river Wey, with the Basingstoke Canal; near Brentford, the Grand Junction Canal; a little below Wandsworth, the Kensington Canal. Pursuing its course through London, it comes to the St Katherine's Docks, and then to the London Docks, a little below which it is passed underneath by a tunnel. It is next joined on the south by the Grand Surrey Canal, and then at Limehouse on the north by the Regent's Canal, and the Limehouse Cut to the river Lea. Proceeding a little, it reaches the western entrance to the West India Docks at the Isle of Dogs, round which it makes a more than semicircular bend, first south to Deptford and Greenwich, and then north again to the eastern or Blackwall entrance to the West India Docks. To avoid or shorten this route, a cut, called the City Canal, was made by government across the isthmus, and after all cutting off little more than half the bend; but so few inclined to avail themselves of such a partial improvement, that this canal was quite neglected, and was latterly sold to the West India Dock Company, who now use it for the wood trade, under the name of South Dock. But before reaching Deptford, the Thames had on its western bank passed the Commercial Docks. At Blackwall it passes the East India Docks, and, at Bow Creek receiving the river Lea, pursues its way to Woolwich, where a short canal is cut to the Arsenal, a little below which it receives the river Roding on the north, and, nearly opposite Purfleet, the river Darent on the south. At Gravesend, the Thames and Medway Canal unites with it; at Sheerness on the south it receives the river Medway, and has now itself become a large estuary, five miles wide, called the Mouth of the Thames, which, expanding greatly, receives from the north and west the rivers Crouch, Blackwater, and Colne.

Owing to the natural obstructions which exist in many parts of the river, from bends, shoals, islands, weeds, &c., the velocity of the Thames does not follow the law of the variation of the inclinations; and the artificial obstacles from weirs, pound-locks, fishing-aytes, &c., render it impossible to ascertain the velocity correctly. Much depends also on the volume of water which may be passing down the river at the time, and the use of flashes. The total fall from Lechlade to low-water mark at London Bridge, a distance of $146\frac{1}{2}$ miles, is 258 feet; being on an average about twenty-one inches per mile. This is overcome by several locks, constructed at different periods, of which the lowest, at Teddington, eighteen miles and three quarters above London Bridge, forms the limit of the tide. In general the velocity may be estimated at from half a mile to two miles and three quarters per hour; but the mean may be about two miles. Between London Bridge and Westminster Bridge the mean velocity of the flood tide is now three miles per hour, maximum three and a half; and the mean ebb three miles and one sixth, maximum three and

---

*A flash is water suddenly let out to increase the depth over a shallow while a boat is passing. It also helps to scour and deepen the channel.* three quarters. Formerly they were much less. The fall from Teddington Lock to London Bridge is only sixteen feet and three quarters, or ten inches and three quarters per mile; for in general the fall gradually diminishes from Lechlade downwards.

The removal of the numerous and bulky piers of the Old London Bridge has wrought an important change in the Thames, not only above or west of the bridge, but likewise, though in a smaller degree, below or east of it. The very contracted spaces through which the water had formerly to force its way occasioned frequently a fall of five feet at low water, instead of which there is now only a fall of about two inches at the new bridge; so that the low-water line above the bridge is nearly five feet lower at spring tides than formerly. In consequence of this, a greatly increased body of tidal water now flows up and down the river, and with a decidedly greater velocity than formerly. The effect of this is to scour and deepen the bed of the river; its influence in this respect being already sensibly felt as far up as Putney Bridge, seven miles and a half above London Bridge. The shores above the latter, that were formerly foul and muddy, are now becoming clean shingle and gravel; and near low water the beach is quite hard and firm. East of London Bridge the shoals are also deepening; and there can be little doubt that the change will at no distant period be felt from the Nore up to Teddington. The depression of low water below the bridge has been so considerable as to cause ships in many instances to ground in their tiers. From a register of the tides, it appears that the average depth at low water on the sill at Shadwell Dock is twenty-two inches below the old mark called Trinity Datum; and where formerly there were eight feet upon the dock sill there are now only six feet two inches on the average. Before the removal of the old bridge, a barge starting from the Pool at Rotherhithe with the first of the flood, could not get farther than Putney Bridge without the assistance of oars or horses. But, under similar circumstances, a barge now reaches Mortlake, four miles farther up, before using oars; and with a little help she may reach Richmond, and, taking horses there, get to Teddington in a tide. The descent down the river has been equally facilitated.

The immense trade of the navigable part of this river arises principally from its having London on its banks, and bearing to and from it numberless ships, fraught with the produce of every country and every climate. Its depth of water is so great, that even at ebb tide it is from twelve to thirteen feet in the fair way of the river above Greenwich. The mean range of the tides at London Bridge is about seventeen feet, whilst at extreme springs it is about twenty-two. Up to Deptford, the river is navigable for ships of any burthen; to Blackwall, for those of 1400 tons; and to the St Katherine's Docks, adjoining the Tower, for vessels of 800 tons.

The Thames and Medway Canal is a cut of about seven miles and a half through the isthmus, or rib of land, between these rivers, and was constructed for the purpose of shortening by forty miles (some say forty-seven) the water communication between Gravesend and Chatham, or Rochester, which had hitherto been by the Nore. It commences in the south bank of the Thames, at Gravesend, nearly opposite Tilbury Fort, where it has a great tide-lock, and a basin and wharfs. From this it runs eastward for about three miles through Gravesend Marshes; then, after turning considerably to the south, it passes through a tunnel of two miles and a half, and proceeds to join the river Medway, where it has another tide-lock and basin nearly opposite to Chatham. The water in this canal is fifty feet wide at top, twenty-eight at bottom, and eight feet deep. The hill through which the tunnel is carried is in some places of such a loose texture that several of the workmen were killed by the unexpected shooting in of the chalk and flints upon them. They had not, it seems, used any precaution to prevent such an occurrence, or to avoid the danger of it. This tunnel, being of large dimensions, and provided with an excellent towing path, has greatly the advantage of many of the miserably confined holes which are carried through hills in other parts of the kingdom. The breadth of the water through the tunnel is twenty-two feet; but a particular description of the locks will be found farther on.

The Thames and Severn Canal commences at the extremity of the Thames and Isis Navigation, near Lechlade, and proceeds by Kempsford and Cricklade to Latton, where it is joined by the Wilts and Berks Canal; thence it passes to Siddington St Mary, at which a branch of a mile goes to Cirencester; continuing westward, it passes through the famous Sapperton tunnel, 4300 yards long, and 250 feet under the top of the hill. From this, it passes to its termination in the Stroudwater Canal, at Wallbridge, near Stroud. The total length is thirty miles and one eighth, viz. from Lechlade to the tunnel twenty miles and three eighths, rising 134 feet by fourteen locks; the tunnel or summit-level two miles and three eighths, and from it to the termination seven miles and three eighths, falling 243 feet by twenty-eight locks. This canal is forty-two feet wide at top, twenty-eight at bottom, and five deep. The locks are eighty feet long and twelve wide.

The Tone and Parrett Navigation commences in the line of the proposed Grand Western Canal at Taunton, and runs nearly north by a bending course, passing Bridgewater, to Start Point, in the Bristol Channel; being, however, joined in its course at Borough Chapel by the Parrett River. The length is about twenty-seven miles.

Trent River begins to be navigable at Burton-upon-Trent, where it is joined by a branch from the Grand Trunk; and which is about 117 miles from the Humber. It proceeds in a north-easterly direction to near Swarkestone, where it receives the Derby Canal, and then at Wilden Ferry it is joined by the Grand Trunk or Trent and Mersey Canal; next by the river Soar or Loughborough Navigation, and opposite to it by the Erewash Canal; then passing Clifton Hall, where the Beeston Cut, which connects with the Nottingham Canal, joins it on the north, it runs down to Nottingham, and there joins the Grantham Canal. Next at Torksey it connects with the Foss-dike Navigation, and at West Stockwith with the Chesterfield Canal and the river Idle. At Keadby it connects with the Stainforth and Keadby Canal, and joining the river Ouse at Trentfalls, their united waters form the Humber. The total descent in the 117 miles is about 118 feet. This river, connecting the port of Hull with a wide extent of country, by numerous rivers and canals, forms a ready medium of traffic for the several very extensive manufacturing and agricultural districts with which it communicates.

The Trent and Mersey Canal, sometimes called the Grand Trunk, from its passing through the central parts of the kingdom and connecting the Trent, Mersey, and Severn, commences at Wilden Ferry, where the Derwent falls into the Trent, and running south-west, passes Aston and Swarkestone, near where it is crossed by the Derby Canal; thence continuing to Burton, where it communicates with the Trent, it passes on to Tradley, and there joins the Coventry and Fazeley Canal. Turning north-west by Rugeley to Heywood Mill, it is there joined by the Staffordshire and Worcestershire Canal. Passing by Weston to Stone, and north by Trentham to Stoke, it is there joined by the Newcastle-under-Line Canal on the south; and the Caldon branch runs from its north side to near Uttoxeter. Continuing north by Etruria, it passes through the new tunnel of 2880 yards at Harecastle, in Staffordshire, which was made only about a dozen years ago, the original tunnel being excessively confined, and without a towing-path. This canal is then joined by the Macclesfield Canal. It next inclines north-west to Middlewich, where the Middlewich branch goes off; then passes near Northwich, and through the three small tunnels of Barnton, Saltersford, and Preston, to its termination at Preston Brook, in the Duke of Bridgewater's Canal. From Wilden Ferry on the Trent, to the Harecastle summit, there is a rise of 316 feet; and from this to Middlewich the fall is 326 feet; the remainder being level to Preston Brook. The total length is about ninety-three miles.

Tyne River is navigable for large vessels in the tide-way for fifteen miles up from its mouth, in the German Sea, to Newcastle, and a few miles farther for a particular kind of barges called keels. The principal trade is in coals, and has for ages been carried on to a great extent.

Ulverstone Ship Canal commences at Hammerside, in Morecombe Bay, in the Irish Sea, and terminates at the new basin and wharfs at Ulverstone; it is about a mile and a half long. The water is sixty-five feet wide at top, thirty at bottom, and fifteen feet deep. It has a tide-lock 112 feet long at its entrance.

Ure River Navigation, or Ripon Canal, proceeds partly up the Ure, from its mouth at Milby, on the Ouse or Yore River, and partly by a canal to Ripon. The length is about eight miles and a half.

The Warwick and Birmingham Canal commences in the Warwick and Napton Canal at Saltesford, in the borough of Warwick, and passing north-west by Bowington to Kingswood, is there joined by the Lapworth branch of the Stratford-upon-Avon Canal; thence, by Knowle, Olton End, and Kingsford, it at length joins the Digbeth branch of the Birmingham Canal at Birmingham. The first half mile is level; the next two and a half to Hatton rise 146 feet by twenty locks; and thence there is a level of eight miles and a half to Knowle Common. Having in the next quarter of a mile risen forty-two feet by seven locks, it then runs ten miles level, and the remainder falls forty-two feet by five locks. The total length is twenty-two miles and a half.

Warwick and Napton Canal extends from the Warwick and Birmingham Canal at Saltesford to the Oxford Canal, near Napton-on-the-Hill, a distance of about fourteen miles, with a rise of 134 feet.

Waveney River, between Suffolk and Norfolk, is navigable for about twenty-three miles from its mouth in the Yore, at Burgh, up to Bungay.

Wear River is navigable from its mouth in the German Sea, at Sunderland, up to near the city of Durham; a distance of about eighteen miles. This navigation is of great importance for the exportation of coal, which abounds in the neighborhood; and in 1830 an act was obtained for various improvements on it.

Weaver River Navigation commences in the tide-way of the Mersey at Weston Point, and proceeds first in a cut for four miles, and then nearly up the course of the river to Winsford Bridge; a total distance of twenty-three miles and three quarters, ascending fifty feet by twelve locks.

Welland River has, by means of locks, weirs, and cuts, been made navigable from its mouth in the Wash, up to Stamford, in Lincolnshire; but the works require to be greatly improved.

Wey River has been rendered navigable from its mouth in the Thames, partly by extensive side-cuts, and partly in the bed of the river, up by Woburn Park and Guildford to Godalming. In fifteen miles and a quarter from the Thames to Guildford it rises sixty-eight feet and a half; and thence to Godalming, which is mostly an artificial canal, the rise is thirty-two feet and a half. The total length is about twenty miles and a half. About two miles from the Thames it is joined by the Basingstoke Canal, and farther on by the following:

The Wey and Arun Junction Canal extends from the Wey, near Shalford Powder Mills, to the Arun Navigation at Newbridge; a distance of eighteen miles. It forms part of the navigable line between London and Portsmouth.

The Wilts and Berks Canal commences at Semington, in the Kennet and Avon Canal, and proceeds by near Melksham, Chippenham, Wootton-Basset, and Wantage, to the Thames at Abingdon; a distance of fifty-two miles. From Derry Hill a branch of one mile and a half goes off to Chippenham; and near Stanley House another of three miles goes to Calne. From near Eastcott a branch of eight miles and a half, originally called the North Wilts Canal, goes to join the Thames and Severn Canal, near Cricklade, with a full of fifty-eight feet and two thirds; and from Breach Field a branch of three quarters of a mile goes to Wantage. In the first seven miles and three eighths to the Chippenham branch the rise is fifty-four feet; thence to the Calne branch, one mile and a half, rising seventeen feet; and thence to the summit-level, ten miles and three quarters, rising 130 feet. The summit extends nine miles and three eighths, and in fifteen miles from it to Wantage River the fall is seventy-one feet and a half; thence to Abingdon, seven miles and three quarters, the fall is ninety-six feet and a half. This canal is an important link in several navigations.

The Wisbeach Canal is a level cut of six miles, from the Nene River at Wisbeach, to the Old River at Outwell, at the end of Well Creek, through which it communicates with the Ouse at Salter's Load Sluice.

Witham River is navigable from its mouth in the Wash, up to the Foss-dike Navigation, at the city of Lincoln; a distance of thirty-eight miles, through a level country, viz. from the sea to Boston five miles, thence to the Sleaford Canal eleven miles, thence to the Horncastle Navigation three miles, and thence to Lincoln nineteen miles. The greater part is embanked on both sides from the sea upwards.

The Worcester and Birmingham Canal commences at the junction of the Birmingham Canal and the Birmingham and Fazeley Canal, at the upper end of the town of Birmingham, and runs south-west to its junction with the Dudley Canal at Selly Oak; thence south-east to King's Norton, where it receives the Stratford-upon-Avon Canal. From this it continues south-west by Stoke Prior, till, a little east of Droitwich, it joins the Severn at Diglis, a little below Worcester. The total length is twenty-nine miles, the breadth at top forty-two feet, and the depth six. In the first fourteen miles the canal is level; but in the remaining fifteen it falls 428 feet by seventy-one locks, which are each eighty-one feet long and fifteen wide. There are five tunnels on this line; that at West Heath is 2700 yards long.

Wreak and Eye Rivers, or Leicester and Melton-Mowbray Navigation, extends from the Leicester Navigation at Turnwater Meadow to the Oakham Canal at Melton-Mowbray, about eleven miles. It follows the courses of the Wreak and Eye.

Wye and Lugg Rivers, the former the principal branch, begins to be navigable ninety-nine miles and a half by water from the Severn, viz. from Hay to Hereford thirty miles, thence to the mouth of the Lugg seven and a half, thence to the town of Ross twenty-one and a half, thence to Lidbrook eight, thence to Monmouth twelve, and thence to the Severn twenty and a half. This river has a considerable declivity; and the great rise of the tides renders the lower part difficult and dangerous.

Wyrley and Essington Canal commences near Wolverhampton, in the Birmingham Canal, and passes by Polesd and Lichfield to the Coventry Canal near Huddlesford, a distance of twenty-four miles. The first sixteen to Can- nock Heath Reservoir are level; in the remaining eight is a fall of 270 feet by thirty locks. There is a branch of five miles and a half to Hay-Head Lime-works; another of two miles and a half to Lords-Hay Collieries; another of four miles to Wyrley-Bank Collieries, with a cut of one mile from it to Essington New Collieries. The canal is twenty-eight feet wide at top, sixteen at bottom, and four and a half deep.

Yare River is navigable from Norwich to Yarmouth by a crooked course of twenty-eight miles. At Yarmouth it is joined by the river Thurn, and at Burgh by the Waveney. This navigation being incumbered by shallows, gave rise to the Norwich and Lowestoft Navigation.

Yore River, see Ure.

Several of the British canals always were, and others are now become, very unproductive. Some have suffered from an ill-advised location, and others have been reduced in value by changes in the course of trade. The rapid progress of manufactures, and the increase of domestic commerce, have invited a resort to new and shorter channels of communication; and not a few costly works are now sustaining an unequal competition with the less expensive productions of more modern art. The day may not be very distant when these will in their turn become unprofitable, and give place to other projects; but they can never cease to be regarded as monuments of skill in mechanical construction. Some of the canals of England are sadly cramped, by the miserably confined state of their bridges, and especially of their tunnels, which are often so low and narrow as to have neither room for a towing-path, nor yet for the boatmen, except lying prostrate, and moving the boat slowly along, by pawing against the walls with their hands or feet. Some excuse might be pleaded for those of this sort which were first made, or which are in obscure districts; but it is remarkable that the tunnel of the Regent's Canal, which passes under a wing of the great metropolis, and was only made in 1819, should have no towing-path.

Ireland.

It has been said that the unfortunate Earl of Strafford, from having seen the utility of inland navigation in the Low Countries, first suggested the improvement of river navigation in Ireland. In 1703 the first act of parliament was passed for rendering the Shannon navigable, and many improvements were projected. Nothing, however, was effected but an useless expenditure of L.140,000 on the Shannon and Boyne in the year 1758. Various other large sums were afterwards granted and frittered away in partial improvements of the Shannon, Boyne, Barrow, and Newry Rivers, besides the Grand, Royal, Kildare, Naas, and Lough Erne Navigations.

The following is a concise account of the principal inland navigations of Ireland, arranged alphabetically; but several others are in progress.

Bandon River, county Cork, is navigable from the port of Kinsale up to within two miles of Bandon.

Bann River, county Down, is navigable for nine miles, from where it is joined by the Newry Canal, near Portadown, to its entrance into Lough Neagh. This is sometimes called the Upper Bann. The outlet of Lough Neagh, called the Lower Bann, is not navigable, but might surely be easily made so, since it has only a descent of thirty-eight feet to the sea, five miles below Coleraine.

Barrow River has been rendered navigable from the tideway below St Malins, up to where it is joined by the Grand Canal at Athy Bridge, a distance of forty-three miles, falling 172 feet. But from Athy to the mouth of the Barrow, in the estuary of Waterford harbour, and through that to St George's Channel, the distance exceeds sixty miles.

Blackwater River, county Cork, is navigable from its mouth at Youghall, up as far as the tide reaches, or at most to Cappoquin. There is another and smaller Blackwater, connected with the Tyrone Canal, and flowing into Lough Neagh.

Boyne River is navigable from the bay of Drogheda for twenty-two miles up to Trim, in the last seven miles of which it ascends from Navan 189 feet, by means of locks, which are from eighty to 100 feet long, and fifteen wide.

Corrib River and Lough or Lake form a navigable line, commencing at the mouth of that river in Galway Bay, and extending from Galway town in a north-westerly direction for about twenty-four miles.

Earne River and Lough or Lake are navigable through the lake, from the upper part, where the river enters it, below Belturbet, till it leaves it again at Enniskillen, where it is obstructed by weirs; but below the isle on which that town is built the river again expands into the lower part of the lake, through which it is also navigable. Thus far the entire distance is about thirty miles, and the navigation is terminated by a fall, from which the river has a rapid course of nine miles to Donegal Bay. It has been proposed to construct a canal from Lough Earne, beginning near Belturbet, and to follow along the valleys of the Finn and Blackwater to Lough Neagh.

Fergus River, county Clare, is navigable from its mouth, in the Shannon, up to Ennis, the county town.

Foyle River is navigable for ten miles from its mouth, in the estuary of Lough Foyle, below Londonderry, up to Strabane.

The Grand Canal commences on the south side of the river Liffey, near its mouth, and proceeds westward by the south side of the city of Dublin, through the counties of Dublin, Kildare, and King's County to the Shannon, with which it unites near Banagher. But, exclusive of this main line of about eighty-seven miles, there is a westerly branch or rather continuation of the line for fourteen miles beyond the Shannon to Ballinasloe, and there is a southerly branch of twenty-six miles from Lawton to Athy, where it joins the Barrow. There are also branches to Naas, Mount Mellick, Portarlington, and other places. The water is forty feet wide at the surface, twenty-five at the bottom, and six deep. The locks on the main line are seventy feet long, fourteen and a half wide, with five feet of water on the sill, and their average lift is nine feet. The track of this canal passing for a considerable way through the bog of Allen added greatly to the expense, which is said to have exceeded two millions sterling. The highest part rises 278 feet above the sea.

Lagan Navigation commences in the tideway at Belfast, and proceeds mostly by the course of the river as far as Lisburn, from which it is continued by a canal, by Hillsborough and Moira, to Lough Neagh. The total length is twenty-eight miles.

Lee River is navigable in the tideway up to the city of Cork, and for small craft somewhat farther. Below Cork, however, the navigation is principally an arm of the sea called Cork harbour.

Liffey River is navigable from its mouth in Dublin Bay for about three miles up to Carlisle Bridge, at the farther end of the city of Dublin. From the south side of this navigable part proceeds the Grand Canal, and from the north side the Royal Canal.

Limerick Navigation commences at that city, and proceeds in a north-easterly direction, partly in the Shannon and partly by canals, for fifteen miles, to Killaloe, at the south end of Lough Derg.

Maig River, county Limerick, is navigable from its mouth in the Shannon to near Adare.

Moy River, county Mayo, is navigable for about five miles, from Killala Bay up to Ballina. Neagh Lough or Lake, being about twenty miles long and ten broad, is generally of sufficient depth to be navigable to a considerable extent in every direction. It communicates with Belfast by the Lagan Navigation, with the Tyrone Collieries by the Blackwater, with Antrim by the Antrim River, and southward with the sea by the Newry Navigation.

Newry Navigation commences in the tideway of Lough Fathom, three miles below Newry, which it passes, and proceeds sixteen miles by a canal to the upper Bann River, in which it continues to Lough Neagh. The entire length is about thirty miles and three eighths, generally in a north direction. It has hitherto been a very imperfect navigation, but was the first executed in Ireland.

Nore River is navigable from its mouth, in the Barrow, two miles above New Ross, for considerable vessels to Innisfree, and up to Thomastown for barges.

The Royal Canal commences at Dublin, on the north side of the Liffey, and proceeds in a direction which generally diverges slightly from that of the Grand Canal, being about west by north for eighty-three miles to its junction with the Shannon at Tarmonbury. The water is forty-four feet wide at top, twenty-four at bottom, and six deep, and the summit is 322 feet above the sea. The locks are eighty-one feet long and fourteen wide. A few years ago this canal was said to be in a sadly neglected state; part of it at Leixlip, eight miles only from Dublin, having scarcely ever been used, and the works apparently fast going to ruin.

Shannon River forms the most important feature in the inland navigation of Ireland. For the first 144 miles of this navigation, viz. from the head of Lough Allen to the sea below Limerick, the Shannon may be considered as a concatenation of rivers and lakes. Issuing from Lough Allen, it passes Leitrim, Carrick, Tarmonbury, &c., and then enters, at Lanesborough, a very irregularly shaped and extensive sheet of water, called Lough Ree, about seventeen miles in length. Leaving it, the river, now greatly augmented, passes Athlone, and then winds by Shannon Bridge and Banagher to Portumna, near which it expands into Lough Derg, another narrow lake, twenty-three miles long, with deep bays and inlets. From the southern extremity of this lake it flows on to Limerick. In this extent of navigation we have, first, Lough Allen, ten miles; thence to Lough Ree, forty-three; Lough Ree itself, seventeen; thence to Lough Derg, thirty-six; Lough Derg, twenty-three; thence to Limerick, fifteen; making together 144 miles. The mean height of Lough Allen above the sea at Limerick is about 143 feet, being on an average about a foot of declivity per mile. Instead of the natural fall, however, the water has been reduced, by means of locks, to a series of level pools. The estuary or frith of the Shannon extends south-west about seventy miles beyond Limerick to its mouth, which is finally about eight miles wide between Loop Head and Kerry Head, at the Atlantic.

The direction of the Shannon from Lough Allen to Limerick, though generally south by south-west, is very circuitous, and broken by many streams, islands, and rocks. The soundings are as various, and both banks are liable to be overflowed by the river to a great extent; and the large expanse of the lakes would require a different sort of vessels from those which navigate the river. The works which have been constructed to overcome the natural difficulties of the navigation are either insufficient or in a state of decay; and it seems to be generally admitted that very little real good can be effected until the natural obstructions are removed, the number of lakes reduced, and the channel deepened and improved in various parts; though it is still doubted if the navigation would even then be suitable for any thing but steam-vessels. The Shannon connects with the Royal Canal at Tarmonbury, and with the Grand Canal at Shannon harbour, near Banagher. At Shannon Bridge it receives, on the west, its principal tributary the Suck; on the east, the Inny, the Upper and Lower Brosna, Mulkena, Maig, Fergus, &c. Much information on this and the other navigations of Ireland will be found in the Parliamentary Reports, particularly those for 1830 and 1834.

Slane or Slaney River is navigable from its mouth in Wexford Haven, for fourteen miles, to Enniscorthy.

Suir or Suir River unites with the Barrow in the estuary called Waterford harbour, about five miles below the town, and is navigable from that up to Carrick for sloops, and to Clonmell for barges. At the town of Waterford, the largest ships lie affloat in forty feet water.

The Tyrone Colliery Canal commences at the southwest extremity of Lough Neagh, proceeding by a short cut across the isthmus of Maghery to the Blackwater River, and, following it a short way, passes by another cut of three miles to the Colliery Basin, from which a railway extends to the mines.

NORTH AMERICA.

United States.

The advantages resulting to the United States from General their separation from the mother country, and the great observation and rapid improvement which has taken place in the condition and circumstances of that republic since the American revolution, are in nothing more strikingly displayed than in the increased facilities of travelling and intercourse between the different parts of the Union, produced by the construction of roads, canals, and railways, and by the improvement of river navigation. But the spirit of enterprise with respect to internal improvement has been chiefly manifested, and has extended more or less to all the states of the Union, since the close of their last war with Britain. For although it is a considerable time since something was first done towards inland navigation in the United States, yet till then comparatively little attention was paid to this by the Americans. Indeed, as long as they were cramped by the narrow policy of the parent country, they had little inducement to undertake any thing of the sort; and from the peace of 1783 till the adoption of the present constitution they had not the means; besides, their peculiar situation and employment during the long wars in Europe rendered internal improvements of this kind less necessary. The experience of the last war between Britain and the United States, and the long peace which succeeded it in Europe, together with the vast expansion of American population, have shown the importance and necessity of such works, as well as others, in that extensive country; and, since the year 1815, the United States have progressed in these improvements with an unexampled rapidity. Most of the canals on the continent of Europe have been constructed at the expense of governments; in England chiefly at the expense of companies or individuals; and in the United States they have been made by the states and by individuals, aided occasionally by the general government. In locating canals in this latter country, two principal objects have been kept in view; one to insure a safe inland communication along the Atlantic border in case of a war with any power possessing a superior maritime force; whilst another and very important object

---

1 Macculloch's Statistics of the British Empire. has been to connect the waters of the western districts with those of the eastern, and thereby facilitate the intercourse between these two distant sections of the country. The vast expansion of population in the western parts, and the great and growing resources of that portion of the Union, have rendered such improvements of great importance, and have created rival interests in the eastern, in order to secure the advantages of this intercourse. The valley of the Mississippi is watered by rivers, some of which, only of the third rate, extend 1000 miles; and it is also indented by lakes the magnitude of which justly entitles them to the appellation of inland seas. Its population is spread over a country unrivalled in the extent and magnitude of its navigable waters, as well as in the fertility of its soil. The navigation of these great rivers, as well as that of many others, which was formerly very difficult, against the stream, has been wonderfully facilitated by the application of steam power, which has enabled the navigator to propel his vessel up the river, and to triumph over the violence of the torrent; and thus the rivers by which great continents are intersected have been rendered doubly valuable in facilitating the inland communications of the country, and in laying open the most remote and formerly sequestered scenes to the inquisitive researches of travellers. With respect to canals, there is no navigable line entirely artificial (for those of China are partly rivers) of such length as the Erie Canal, which is 363 miles, and was formed in about eight years. That of Languedoc, in France, is only 148 miles, and occupied fourteen years in construction, even during the reign of Louis XIV. However, the great canal of Amsterdam, in Holland, though only fifty miles long, contains twice as much water as the Erie Canal.

The aggregate length of canals now finished in the United States exceeds 2000 miles; but some of the states do not admit of their construction, except to a comparatively small extent, whilst others present a vast field and great inducements for prosecuting such works on a magnificent scale. Our limits, however, will only admit of a very brief description of these improvements; and to this we shall now proceed, following the order in which the states are usually arranged, and omitting of course such of them as are not possessed of canals.

The Cumberland and Oxford Canal, twenty miles and a half long, extends from the tideway near Portland to Sebago Pond. It has twenty-six locks, and was completed in 1829. By means of a lock in Songo River, the navigation is continued into Brandy and Long Ponds, making in all fifty miles. Improvements have been projected in the navigation of the river St Croix and the adjacent waters. It has also been proposed to construct a canal from the mouth of the Sebasticoock River, near Waterville, on the Kennebeck, to Moosehead Lake.

Several canals have been constructed around falls in the New Hampshire, Merrimack. Bow Canal, one third of a mile in length, three miles below Concord, with four locks, passes a fall of twenty-five feet. Hooksett Canal, fifty rods long, with three locks and a lockage of sixteen feet, passes Hooksett Falls. Amoskeag Canal, with nine locks and a lockage of forty-five feet, passes Amoskeag Falls, nine miles below Hooksett Falls. Union Canal, immediately below Amoskeag, overcomes seven falls in the river, and has seven locks in nine miles. A canal is now in progress around Sewall's Falls, in Concord.

The Middlesex Canal, connecting Boston harbour with the Merrimack at Chelmsford, two miles below Lowell, opens a water communication between Boston and the central parts of New Hampshire, and is twenty-seven miles in length. It has twenty locks, with a lockage of thirty-six feet; and is thirty feet wide at top, twenty at bottom, and three feet deep. It was completed in 1808, and was then the largest in the United States.

Blackstone Canal, extending from Worcester to Providence, in Rhode Island, is forty-five miles long.

The Hampshire and Hampden Canal, extending from the boundary of Connecticut in Suffield, to Northampton, is twenty-two miles long, and, forming a continuation of Farmington Canal, which is fifty-four miles in length, makes the whole line from Newhaven to Northampton seventy-six miles.

Montague Canal, for passing the falls in the town of that name, is three miles in length; and South Hadley Canal, around falls in the town of South Hadley, is two miles in length.

Farmington Canal, fifty-four miles long, commences at Newhaven, passes through the valley of Farmington River, cut, and at the boundary of the state of Massachusetts it unites with the Hampshire and Hampden Canal, which reaches to Northampton, and is twenty-two miles in length. Enfield Canal, five miles and a half long, is constructed around the Enfield Falls in Connecticut River.

The Erie Canal, extending from Albany on the Hudson River to Buffalo on Lake Erie, a total distance of 363 miles, is one of the greatest and most important works of the kind in the world. It was projected by an American patriot, Mr De Witt Clinton; commenced in 1817, and finished in 1825. The water is forty feet wide at the surface, twenty-eight at the bottom, and four feet deep. These are generally the dimensions of the other canals in this state, and therefore they cannot carry very heavy boats; but a less depth will always suffice if the boats are not encumbered with keels, which are utterly useless in a canal. The western section, from Buffalo on Lake Erie to Montezuma on Seneca River, is 157 miles in length, with twenty-one locks for a fall of 186 feet; the middle section, from Montezuma to Utica, is ninety-six miles, with eleven locks for a rise and fall of ninety-five feet; the eastern section, from Utica to Albany, is 110 miles, with fifty-two locks for a fall of 417 feet; total length 363 miles, with eighty-four locks for a total rise and fall of 698 feet. Lake Erie is 565 feet above the Hudson River at Albany. The average rise or fall of eighty-one of the locks is eight feet and a half, the other three are regulating or guard-locks.

This canal forms a channel by which the trade of the great inland waters of Lake Erie, Lake Huron, Lake Michigan, &c. may find access to markets in the populous cities of Eastern America and of Europe. Indeed there is already such a traffic on this canal and its branches, described below, that it has been proposed greatly to increase its dimensions, which must require many times the additional expense necessary to have made it sufficiently large at first. There is, however, nothing very remarkable in this, because the most proper size of a canal can seldom be foreseen by the projectors.

Champlain Canal, sixty-three miles long, commences, at its junction with the Erie Canal, nine miles north of Albany, and terminates at Whitehall, on Lake Champlain, in Washington county, thus connecting the Erie Canal and the Hudson River with Lake Champlain. It has seven locks for a rise of fifty-four feet from the lake to the summit-level, and fourteen locks for a fall of 134 feet from this to the Hudson, in all twenty-one locks; the rise and fall are 188 feet. It has a lateral cut connecting it with the Hudson by three locks at Waterford, eleven miles north of Albany, similar to the cut connecting the Erie Canal with the same river at West Troy by two locks.

The Oswego Canal, of thirty-eight miles, from Salina to Oswego, connects Lake Ontario with the Erie Canal. Half the distance is canal and half slack-water or river navigation. It has fourteen locks, thirteen of stone and one of wood and stone, for a fall of 123 feet from Salina to Lake Ontario. The Cayuga and Seneca Canal commences at the Erie Canal at Montezuma, Cayuga county, and terminates at Geneva, Ontario county, connecting the Erie Canal with Seneca Lake. It has also a lateral branch to East Cayuga village on the Cayuga Lake, being thus connected with that lake. It opens altogether a lake navigation of more than a hundred miles. The length is twenty miles and forty-four chains from Geneva, on the Seneca Lake, to Montezuma on the Erie Canal. It is half canal and half slack-water navigation, and has eleven wooden locks for a fall of seventy-three feet from Seneca Lake to the Erie Canal at Montezuma.

The Chemung Canal extends from the head of the waters of Seneca Lake to Chemung (or Uiong) River, a branch of the Susquehannah, at the village of Elmira, Tioga county. The length is twenty-two miles and a half, with a navigable feeder of thirteen miles and a half from Painted Post; Stuben county, on the Chemung River, to the summit-level; total, thirty-six miles. This canal connects the Erie Canal with the Susquehannah River. It has fifty-two wooden locks, with 516 feet of lockage, and one guard-lock.

The Crooked Lake Canal extends from Penn Yan to Dresden, both in Yates county, connecting the Crooked and Seneca Lakes. It is eight miles long, and has 260 feet of lockage, with twenty-seven wooden locks, and one guard-lock.

The Chenango Canal extends from Utica to Binghamton, a distance of ninety-seven miles, with 109 locks. It has sixteen miles of navigable feeders.

The Delaware and Hudson Canal extends from the Hudson River at Kingston, to Port Jervis on the Delaware, fifty-nine miles; thence up the Delaware to the mouth of the Lackawaxen River, twenty-four miles; thence in Pennsylvania to Honesdale, twenty-six miles; total, 109 miles. From Honesdale a railway of sixteen miles and a half, with five inclined planes, rising 800 feet, extends to the coal mines at Carbondale on the Lackawana.

Haerlam Canal, of three miles, intended to connect the Hudson and East Rivers, is begun, but not completed. Chittenango Canal, connecting that place with the Erie Canal, is one mile and a half long, with four locks. Sodus Canal, intended to connect Seneca River with Great Sodus Bay on Lake Ontario, was projected in 1829, and will be twenty-five miles long. Scottsville Canal, intended to connect the Genesee River with Scottsville, in Monroe county, was projected in 1829. The Oneida Lake Canal, of eight miles and a half, intended to connect Oneida Lake with the Erie Canal, was put under contract in 1833. Auburn and Owasco Canal, intended to connect Auburn with Owasco Lake, was projected in 1832, and is to be three miles in length.

It has been proposed to connect by railways or canals the Erie Canal, somewhere about Rome or Herkimer, with the waters flowing into the St Lawrence at Ogdensburg.

The Genesee and Alleghany Canal. The projectors of the Erie Canal contemplated its connection with the river Ohio, by a south-west branch, uniting with the river Alleghany at Olean, in Cattaraugus county. A report of a survey of the line was made to the legislature in 1829. The length from Rochester along the valley of the Genesee to Olean, including navigable feeders, is to be 107 miles, which, with a side-cut to Danville of fifteen miles and a half, make the total length 122½ miles, with 1057 feet of lockage.

The Black River Canal is proposed to extend from the Erie Canal at Rome to the foot of High Falls on Black River, a distance of about thirty-five miles, with improvements in the navigation of Black River from the High Falls to Carthage, a farther distance of forty miles.

A steam-boat canal from Lake Ontario to the Hudson has been proposed, extending from Oswego to Utica, and thence along the Mohawk to the Hudson. A steam-boat or a ship canal has likewise been proposed around the Falls of the Niagara. The longest proposed route would be fifteen miles, with a lockage of 320 feet; a second route would be nine miles, with the same lockage; and a third only seven miles and a half. A ship canal around these falls, on the Canadian side, called the Welland Canal, has been in operation for several years, and will be noticed hereafter.

Delaware and Raritan Canal extends from Bordentown New Jersey to New Brunswick, forty-three miles. A navigable feeder from Boil's Island to Trenton is twenty-four miles long. Morris Canal, extending from Jersey city to Easton, is 101 miles long. Salem Canal, from Salem Creek to the Delaware, is four miles long.

During the last eight or nine years, Pennsylvania has engaged in works of internal improvement more extensively than any other state in the union; and the Pennsylvania Canal and Railway, extending from Philadelphia to Pittsburg, a distance of 395 miles, is the most magnificent work of the kind which has yet been completed in any part of the United States. It consists of the following parts:

| Description | Miles | |-----------------------------------------------------------------------------|-------| | 1. Columbia Railway, from Philadelphia to Columbia | 81-60 | | 2. Pennsylvania Canal, central division, or eastern and Juniata divisions, from Columbia to Hollidaysburg | 171-75 | | 3. Alleghany Portage Railway, from Hollidaysburg to Johnstown | 36-69 | | 4. Pennsylvania Canal, western division, from Johnstown to Pittsburg | 105-00 |

Total: 395-04

1. Columbia Railway commences at Philadelphia, passes Downingtown and Lancaster, and enters Columbia, on the Susquehannah, by an inclined plane 1720 feet in length. It has thirty-one viaducts, seventy-three stone culverts, and eighteen bridges. It attains its greatest height at Mine Ridge, which is 555 feet above tide-water in the Delaware.

2. The central division of the Pennsylvania Canal commences at Columbia; follows the east bank of the Susquehannah, crossing the Union Canal at Middletown; passes Harrisburg; crosses the Susquehannah at the head of Duncan's Island; and enters the valley of the Juniata, which it follows to Hollidaysburg. It has thirty-three aqueducts, and 111 locks.

3. The Alleghany Portage Railway, connecting the central and western divisions of the Pennsylvania Canal, commences at Hollidaysburg, passes over the range of the Alleghany Mountains, and terminates at Johnstown. It has one tunnel through a mountain ridge, and ten inclined planes, with stationary engines, five on each side of the summit-level, their total length being 4-37 miles. The total rise and fall is 2570-29 feet.

4. The western division of the Pennsylvania Canal commences at Johnstown, traversing the valley of the Conemaugh, Kiskiminetas, and Alleghany Rivers, and terminates at Pittsburg. It has sixty-four locks, sixteen aqueducts, sixty-four culverts, 152 bridges, and a remarkable tunnel about 1000 feet long.

The Beaver Canal extends from the town of Beaver, at the entrance of the Beaver River into the Ohio, to Newcastle, and is twenty-five miles long. The Mahoning and Beaver Canal, extending from Newcastle in Pennsylvania to Akron in Ohio, on the Ohio Canal, is now in progress. The Pittsburg and Erie Canal, of which the Beaver Canal is a part, is intended to connect the Pennsylvania Canal at Pittsburg with Lake Erie, and is to be seventy-three Navigation, Inland.

There are various other canals in this state, besides some which are in progress, and others which are only projected.

The Chesapeake and Delaware Canal, which connects the Delaware River with the head of Chesapeake Bay, is partly in Delaware and partly in Maryland, and commences at Delaware city, about forty-two miles below Philadelphia. The length is 13-63 miles, the breadth at top sixty-six feet, and the depth ten feet.

The Chesapeake and Ohio Canal, begun in 1828, commences at Georgetown, on the Potomac, in the district of Columbia, and extends to Harper's Ferry. Its course, as laid out, extends to Cumberland on the Potomac, thence by Will's Creek, Youghiogheny, and Monongahela Rivers, to Pittsburg. The total length, as proposed, is 341 miles and a half, and the lockage 3215 feet. It requires a tunnel through the Alleghany Mountains of four miles and eighty yards. Port Deposit Canal, ten miles long, is designed to overcome the rapids of the Susquehannah above Port Deposit. The Chesapeake and Delaware Canal has been already noticed.

The Canal of Dismal Swamp commences at Deep Creek, about seven miles above Norfolk, and proceeds southward about thirteen miles to the boundary of this state, beyond which it is continued about nine miles in North Carolina, to Joyce's Creek, a branch of the Pasquotank. This canal is thirty feet wide at bottom, and eight deep. Very extensive improvements have been projected and partly executed on the river navigation of Virginia, by means of lateral canals or side-cuts. One on James River extends from Richmond for twenty-three miles up the side of that river, and then joins it again. There are various side-cuts on the Roanoke; one extends about twelve miles from Weldon upward, but that is after the river has got into North Carolina.

Dismal Swamp Canal, already mentioned amongst those of Virginia, enters about nine miles into North Carolina; and Lake Drummond Canal, five miles long, is a navigable feeder of it. North-west Canal, six miles long, connects North-west River with Dismal Swamp Canal. Weldon Canal, twelve miles long, forms the commencement of the Roanoke Navigation, extending around the falls of the Roanoke above the towns of Weldon and Blakely. The navigation of the Roanoke from the Weldon Canal to the town of Salem in Virginia, a distance of 232 miles, as likewise the Cape Fear, the Yadkin, the Tar, the Catawba, and New Rivers, have been greatly improved.

Santee Canal, twenty-two miles long, connects the harbour of Charleston with the Santee. By means of this and the Santee and Congaree Rivers, the navigation of which has been improved, a communication is opened between Charleston and Columbia. The navigation of the Catawba has been improved by five small canals of two, one and a quarter, two and a quarter, one and three quarters, and four miles. Saluda Canal, of six miles, extends from the head of Saluda Shoals to Granby on the Congaree. Drehr's Canal, of one mile and a third, is designed to overcome a fall of 120 feet in the Saluda River. Lorick's Canal, on Broad River, one mile and a half above Columbia, is a mile long; and Lockhart's Canal, in Union District, around Lockhart's Shoals in Broad River, is two miles and three quarters in length.

The Savannah and Ogeechee Canal, sixteen miles long, extends from the city of Savannah to Ogeechee River. An extension of this canal to the Altamaha, sixty miles, is proposed.

Huntsville Canal, from Triana on the Tennessee, to Huntsville, is sixteen miles long. A canal of thirty-seven miles, from the head of the Muscle Shoals to Florence, is considerably advanced, but not yet completed.

A ship canal, of eight miles, has been projected at New Orleans, to lead from the Mississippi to the ocean. It is to commence about three miles below Fort Jackson, and pass through the prairie on the left bank of the river. Besides, there are in progress the Orleans Bank Canal, of four miles and a quarter, from New Orleans to Lake Pontchartrain; the Carondelet Canal, of two miles, which likewise connects New Orleans with Lake Pontchartrain, through the river or bayou St John, which is four miles, making the whole line six miles; and the Barataria Canal, proceeding from the Mississippi, six miles above New Orleans, to the Lafourche, thence through the lakes to Berwick's Bay, and thence to the sea by Barataria. It consists of four parts, amounting to twenty-two miles, which connect an extensive river navigation. The whole exceeds ninety miles.

Kentucky River Navigation, in the course of being executed, viz. the part of that river about to be rendered navigable by locks and dams, extends from its mouth up to where it branches into the three forks. For about 250 miles the whole will be slack water, adapted for steamboats of 150 tons burden. The locks are to be 175 feet long by thirty-eight wide in the chamber, ten feet above the dam; the depth of water is to be six feet; the lift of the locks from twelve to sixteen feet; the dams from twenty to twenty-five feet high, and from 400 to 500 long, and about seventy feet at the base. A variety of improvements, some of them of considerable extent, on other river navigations in this state, have also been projected, and are partly in progress.

The Ohio Canal, which extends from Cleveland upon Ohio Lake Erie, to Portsmouth on the Ohio River, is 397 miles long; it was begun in 1825, and completed in 1832. The summit-level is 305 feet above Lake Erie, 499 above the Ohio at Portsmouth, and 973 above the Atlantic. It has 152 locks for a lockage of 12,050 feet. The distances along this canal, beginning from Cleveland, are, to Akron thirty-eight miles, New Portage nine, Massillon twenty-one, Bolivar twelve, New Philadelphia fourteen, Gnadenhutten thirteen, Coshocton twenty-six, Newark forty, Bloomfield fifty-two, Circleville eleven, Chillicothe twenty, Piketon twenty-four, Portsmouth twenty-seven. It has three navigable feeders, amounting to thirty-three miles.

The Miami Canal, which extends from Cincinnati to Dayton, is sixty-nine miles long; it was begun in 1825, and finished in 1830. The summit at Dayton is 175 feet above the Ohio at Cincinnati. It has thirty-two locks for a lockage of 296 feet. This canal is now in the course of being extended along the valleys of the St Mary's and Au-Glaze Rivers, and is to be united at Defiance with the Wabash and Erie Canal, which extends from Lafayette on the Wabash River in Indiana, to near the entrance of the Maumee into the west end of Lake Erie. It is 187 miles long, and is nearly completed. The whole extent of this united line, from Cincinnati to Lake Erie, is about 265 miles, of which 105 are in Indiana.

The Mahoning and Beaver Canal, now in progress, extends from Newcastle, in Pennsylvania, on the Beaver division of the Pennsylvania Canal, to Akron on the portage summit of the Ohio Canal. It is eighty-five miles in length, but of this eight miles are in Pennsylvania. Sandy Creek and Little Beaver Canal, also in progress, extends from Bolivar on the Ohio Canal, in an easterly direction, to the Ohio River. Various other extensive navigations have been projected in this state, and companies have been formed for carrying them into execution.

Several extensive canals and river navigations have been Indiana-projected in this state, and are partly in progress. We have already mentioned the Wabash and Erie Canal, of which part is in Ohio.

The Illinois and Michigan Canal, now in progress, ex-Illinois- extends from Chicago on Lake Michigan, to Ottawa on Illinois River, a distance of about ninety-five miles. It is to be sixty feet wide at the surface, thirty-six at the bottom, and six deep. About twenty-four miles of this line are to be cut from seven to twenty-eight feet deep, through solid rock. Other canals have been projected in this state.

The Washington Branch Canal, of one mile and a quarter, connects the Chesapeake and Ohio Canal with the Potomac at Washington. The Alexandria Canal, of seven miles and a quarter, extends from that town to the extremity of the Chesapeake and Ohio Canal at Georgetown.

It has been proposed to connect the Atlantic Ocean with the Gulf of Mexico, by a canal across the northern part of the peninsula of Florida.

Some considerable works for promoting inland navigation have likewise been executed in Canada. Of these the following are the principal ones.

The Rideau Canal commences in about long. 75.35. E., and lat. 45.20. N., at Entrance Bay, in the Ottawa River, about a mile and a half from where the Rideau River falls into it, 128 miles from Montreal, and 130 from Kingston on Lake Ontario. It is not so properly a canal as an artificial concatenation of natural lakes. The general direction is south-westerly, to its termination at Kingston; and the total length of the navigation is 132 miles, of which about twenty only are artificial cuts connecting Rideau River and Lake, Mud Lake, Cranberry Lake, and Kingston Mill-Stream. The difference of level is 445 feet, with forty-seven locks, which are each 142 feet long, thirty-three broad, and five deep. This canal, it has been fancied, would be of immense importance for the conveyance of military stores; but this seems to proceed on the assumption that the enemy is to be perfectly torpid during the half year in which the canal is useless from being frozen.

The Welland Canal, connecting Lakes Erie and Ontario, communicates with the latter by the Twelve-mile Creek, and thence ascends the barrier of Lake Erie, near the Falls of Niagara, by means of locks, till it meets the Chippawa, which it ascends for some length, and then joins the Ouse at about a mile and a half from its entrance into Lake Erie. The shifting bar at the mouth of this river has been remedied by extending piers into the deep water. A safe communication between these great lakes is thus effected by this navigation, which is forty-one miles long; the artificial part being fifty-six feet wide, and eight and a half deep. It has thirty-seven wooden locks, each 100 feet long and twenty-two feet wide, overcoming a height of 330 feet. A much shorter canal for passing round the Falls of Niagara has been proposed on the American side.

Grenville Canal consists of three detached parts, of the nature of side-cuts, or lateral canals; one at the Long Sault on the Ottawa, another at the fall called Chute à Blondel, and the third at the Carillon Rapids. This canal renders the navigation of the Ottawa between the Rideau and Montreal complete; but unfortunately some of the earlier constructed locks are only twenty feet wide.

La Chine Canal is a cut of seven miles across the southeast corner of the island of Montreal, to avoid some difficult parts of the St Lawrence, particularly the rapid of St Louis. It is forty-eight feet wide at top, twenty-eight at bottom, and five feet deep, with a fall of forty-two feet; but the locks only admit boats twenty feet wide.

By means of these great and useful works, a large extent of country is opened up to the industry of settlers. There is a continuous steam-boat communication in Upper Canada of about 460 miles, from the Grenville Canal, on the Ottawa, to Niagara. Many other canals are now in contemplation, such as that projected between the bay of Quinté and Lake Huron. A great deal of information regarding the inland navigation of Canada will be found in the Parliamentary Reports, and a more compendious account of it in Martin's History of the British Colonies.

The navigable rivers and lakes of North America are numerous and important, several of them being of vast extent. But a very general feature in such of its rivers as fall into the Atlantic, is a bar obstructing their mouths. That of the principal mouth of the Mississippi had, in 1722, about twenty-five feet of water upon it; Ulloa, in 1767, found twenty-feet at the highest flood; and in 1826 the depth was only sixteen feet. Above these obstructions the rivers are generally much deeper, the Mississippi at New Orleans being above 100 feet deep, which depth it preserves to the mouth of the Missouri. Mobile Bay is crossed by a bar having only ten feet of water; and the bar of the Altamaha of Georgia has fourteen feet, which is perhaps about the average depth to be found at the entrance of most of the southern rivers of the Atlantic coast.

Lake Superior, in the great central plain of this continent, is the largest body of fresh water on the globe. The outlet of this, and of the other great lakes of Canada, forms the river St Lawrence, which is of vast dimensions, the tide flowing up it for 400 miles, and affording navigation for the largest vessels the whole of this distance; but above this the current is extremely rapid. Several of the most difficult parts have already been avoided by means of side-cuts and locks, particularly the rapid of St Louis; and others may be disposed of in a similar manner. Vessels of 600 tons ascend to Montreal, and boats all the way to Lake Ontario, and thence to Lake Erie through the Welland Canal. The Connecticut is a large navigable stream entering the sea near the north-eastern extremity of Long Island. The Hudson has enabled New York to extend its commerce by the Erie Canal to the lakes, being navigable to 160 miles above its mouth for large steam-vessels. The Delaware and its tributaries afford a navigation over an extent of 300 miles in length and breadth. The Susquehannah, the Potomac, and others falling into the Chesapeake Bay, together with canals, afford navigation for vessels of one sort or other into the remotest valleys and recesses of the eastern country. The Roanoke, which falls into Albemarle Sound, together with the Pamlico, afford a medium of commerce for North Carolina; whilst the Pee Dee, Santee, Savannah, Ogeechee, Altamaha, &c. are so many canals intersecting South Carolina and Georgia in all directions. The St John, again, affords a similar convenience for East Florida. But although the eastern rivers have been by much the longest employed for the purposes of navigation, they are in many respects inferior to the immense streams which intersect the western and inland states, particularly the Mississippi and its tributaries, which have no parallel in any other country possessed by a people sufficiently intelligent to turn the commercial facilities of its inland waters to proper advantage. The Mississippi is navigable for 3000 miles up from its mouth to the Falls of St Anthony, and extends over fifteen degrees of latitude. At St Louis it receives the Missouri, which above that junction is greater than the other branch, which still bears the name of Mississippi. The principal tributaries of the Missouri are the Osage, Grand River, Kansas, Platte,

---

1 Canals, it is true, which are all on one level, as is the case in Holland, may become convenient roads whilst the ice is sufficiently strong; but where locks occur, and are so numerous as on this canal, they form a serious obstruction; and it is besides considered necessary in America to have canals as empty as possible during the frost. White River, Chien, Yellow Stone Rivers, each of which on an average adds 1000 miles to the navigation; and there are many others of less note. Above the junction of the Missouri the Mississippi receives, from the east, in latitude 37°, the Ohio, which is of great importance, as affording a direct communication with the eastern states, and being, besides, the channel of a great inland commerce. About 1200 miles from its mouth the Ohio receives, near Pittsburgh, the Monongahela and the Alleghany Rivers. It is connected with Lake Erie by means of the Ohio Canal, and has fifteen large navigable tributaries. The other principal tributaries of the Mississippi more to the north, and each navigable 400 or 500 miles, are the Illinois, Des Moines, Rock River, and St Peter's, between some of which and the great northern lakes there are only short portages. Besides all these, North America contains a vast number of other navigable rivers, which our limits will not admit of our describing.

SOUTH AMERICA.

The vast region of South America, though it has hitherto been kept in a sadly degraded state, by priestcraft, ignorance, slavery, and incessant wars, possesses a conformation peculiarly favourable to an extensive inland navigation. The Andes skirt its western shore, and, though ascending to a great height, are yet so small in breadth as to leave between them and the eastern coast a vast extent of comparatively flat country, divided into the basins of the Orinoco, Amazon, and Paraguay, none of which is much elevated above the sea; and even the dividing ranges between them are generally of very trifling altitude. Thus the Orinoco is navigable, without difficulty, for 260 leagues, to the falls or rather rapids of Atures, where, according to Humboldt, its mean height above the sea does not exceed 350 feet; and thence, after two short portages, it is navigable for above 100 leagues more, to the point near Esmeralda, where the celebrated bifurcation of this river takes place, and a portion of its waters descends along the natural canal of Casiquiare, to join the Rio Negro and the Amazon. On both sides, along its course, the Orinoco receives many tributaries; of which three in particular, the Apure, Meta, and Guaviare, flowing from the westward, have also long navigable courses. The Amazon, again, is navigable to a little above Urarina, near the confluence of the Guallaga, a distance of 750 leagues from its mouth, flowing uniformly along the whole extent, in a direction from west to east, and receiving many tributaries on both sides. By the Napo, Putamayo, and Japura it is connected with the higher districts of Columbia; its own upper navigation, which is uninterrupted above Santiago, connects it with Upper Peru; and the Guallaga and Ucayale descend to it from the south-west, along the eastern face of the Andes, from distances, as it is said, of from 300 to 500 leagues. By the Rio Negro, as already noticed, its waters communicate with those of the basin of the Orinoco; the Rio Branco ascends from this also to within a short and nearly level distance of the sources of the rivers Essequibo and Demerara; and its southern tributaries, rising in the Campos Pareceis (the mean level of which west of Villa Bos, and in about 16° south latitude, where the waters divide, is not probably above 2500 feet), approach so closely to the sources of the Paraguay and its feeders, that near Villa Bella, in Matto-Grosso, only a short portage of three miles divides the course of the Agumpehy, falling into the Jaura and Paraguay, from that of the Guaire, joining the Madeira and Amazon; and, lastly, the Paraguay itself is navigable through nineteen degrees of latitude, from the confluence of the Jaura in 16° 20' south, to its mouth in the Rio de la Plata, near Buenos Ayres, in 35° south lat., and receives also many tributaries along its course, of which four only need be cited, viz. the Parana and Uruguay from the eastward, rivers each nearly equal to the main trunk in value and importance; and from the west the Pilcomayo, said to be navigable with very little interruption as far as Chuquisaca; and the Vermejo, in which there are three fathoms as high as the junction of the Rio Grande, and large boats ascend beyond it as far as Tarigua.

From these facts, then, it appears that, with the exception of one short portage of three miles, water flows, and is for the most part navigable, between Buenos Ayres, in 35° south, to the mouth of the Orinoco, in nearly 9° north latitude. The distance across the continent from east to west, through which the same convenience exists, varies greatly in different lines; but in the basin of the Orinoco it is not under 400 leagues, in that of the Amazons it is nearly 1000, and in that of the Paraguay it varies probably from 200 to 500. That all the interior provinces of South America would be prodigiously benefited by advantage being taken of these facilities for internal communication, cannot admit of a doubt; but the districts which are at present the most secluded, and which would be most strikingly improved by it, are those of Moxos, Chiquitos, and Santa Cruz de la Sierra, which contain about 48,000 square leagues, and produce a great variety of valuable articles, which are unavailable on account of there being no method of transporting them. The only seaport with which they have any communication is Lamar (Cobija), on the Pacific, although the junction of the Jaura with the Paraguay, where the latter becomes navigable, is only seventy leagues from Santa Anna, the capital of Chiquitos, a hundred from Santa Cruz de la Sierra, and seventy-three from Villabella in Matto-Grosso.

It has long been proposed to form a communication between the Atlantic and Pacific Oceans, by means of a canal across the Isthmus of Panama. A very interesting account of a survey of a line across the isthmus, which was made a few years ago by Mr J. A. Loyd, will be found in the Philosophical Transactions for 1830; and some account of a different line by the Lake of Nicaragua is given by Captain Philips in the Journal of the Royal Geographical Society (vol. iii. 275). There can be no question that a ship canal, if practicable, would be greatly preferable to any other equally slow communication; and a railway, again, better than a small canal. A line partaking of both is also talked of.

TUNNELS, LOCKS, &c.

Canals formed for navigation are generally upon a dead level from lock to lock, except when they are also intended for conveying water, whether to other parts of the navigation, or for some different purpose. Feeders or conductors of water to canals should always have a certain declivity; but even in these it is not customary to give the bottom a greater descent than four inches in the mile. The simplest mode of constructing a canal over level ground, is to form it partly by excavation and partly by embankment; that is, to proportion the depth of digging such, that the stuff thrown out shall exactly embank or raise the sides sufficiently to make the canal of the required dimensions. This is called level cutting. But when a canal runs along the side of a declivity, the one bank will require more raising than the other; or the cutting may be all at one side, and the embankment only at the other. If, again, the surface of the ground is undulating, the case becomes more complicated; but it is always a desideratum in the formation of canals, that the stuff excavated from one part may, with the least labour or shortest carriage, exactly supply or form the embankments that are to be raised in another; so that, at the completion of the work, as few spoil-banks or mounds of useless soil as possible may remain, and as little ground as possible be rendered useless by excavations or pits. However, the great expense of rock-cuttings, and other difficulties, often occasion a wide departure from this rule. For, in conducting a canal across a hilly and rugged country, there are many difficulties to be overcome, much levelling, and many works of art to be executed. Some of these, perhaps, cannot be foreseen till the operations have been commenced or are far advanced. The slopes of the banks are regulated by the quality and difference in the tenacity of the soil; but they are seldom made greater than two feet of perpendicular to three of horizontal measurement, particularly where the embankments are heavy.

The inside slope soon becomes chafed and indented at its upper edges by the motion of the water, which is occasioned by the passing of boats; and this abrasion often penetrates so much as to diminish irregularly the width of the towing-path. This may be remedied in a good measure by planting the sides with aquatic shrubs, and also by driving stakes into the bank at short intervals along the water line, so as to form a rude wicker-work, in places where the soil is loose and porous. The Caledonian Canal is provided with a break in the slope for this purpose, as was mentioned in the description of it. But the most effectual protection against the action of the water is attained by walling or paving the sides of the canal for some breadth both above and below the water line. This, however, from its being expensive, has not yet been extensively resorted to; but when it is recollected that the washing of the banks of a canal not only destroys its security, but diminishes its depth and the facility with which it is navigated, this reason loses its weight. By facing the sides with a substantial wall, which might be made nearly vertical at the top, the surface of the water need not be much more than two thirds the usual width, and consequently the canal need not occupy much more than three fourths the extent of ground; so that in situations where the ground is valuable, the wall would conduce to economy. The canal, too, having less earth crumbling into it, would need less cleaning; and where water is scarce, the smaller waste by evaporation, from the contracted breadth of the surface, would be of importance. To prevent as much as possible the wash, as it is termed, the speed of the canal-boats is variously restricted, and steam-boats have generally been excluded.

It frequently happens that canals have to be formed more or less by artificial embankments of loose materials, or that they are excavated in earth, sand, rock, &c., so very porous as to allow the water to escape by filtration. To remedy this, the usual method is to make the excavation much wider and deeper than the intended dimensions, and to line it to the thickness of two or three feet with a tenacious clay mixed with gravel, which is to be thoroughly puddled, and then, according to some, exposed for a long while to the weather, though others condemn exposing it at all. A trench four feet in width is also dug out in the middle of each side-bank, to at least three feet below the bottom of the canal, and this in like manner is to be filled up with paddle. The puddle trench is made principally with the view of preventing rats and other vermin from perforating the banks, and occasioning breaches, as they often do. When once the water has obtained a very small egress, it gradually washes it wider; so that sometimes in a few hours a breach may be formed sufficient to empty the canal, and require weeks or even months ere it can be repaired. But besides being able to resist the penetration or gradual escape of the water, an embankment must always be composed of materials capable of withstanding, by their weight, the tendency of the hydraulic pressure to overturn them in a mass, and also of resisting, by their lateral adhesion, the force tending to thrust them out horizontally. When the side of a canal gives way, it is of great consequence to prevent as much as possible the escape of the water. For this purpose, it is usual to have doors or valves in various parts of the canal, so attached by joints or hinges to the bottom, that when the water is at rest they lie nearly flat at the bottom, but when it begins to flow rapidly over them, they rise by its force, and arrest its farther progress. However, when such gates have lain long in the bottom, and have become coated with slime and imbedded in the mud, their spontaneous rising at the proper time is not much to be depended on, and therefore they should be provided with chains or rods, by which they may be drawn up when required.

Tunnels.

The first thing to be attended to in constructing a tunnel is to execute a correct survey of the ground through which it is intended to pass. This is done by tracing over the surface of the ground a line which shall be all in a vertical plane parallel to the direction of the tunnel, and which, when transferred upon a reduced scale to paper, shall accurately represent a vertical section of the ground. To obtain a section of this sort with accuracy for an extensive tunnel, the relative levels of the principal points along the line upon the surface are to be ascertained; and it is generally necessary to use an instrument similar to a transit telescope, and perhaps to fit up one or more temporary observatories upon the most elevated spots along the line, from which may be determined the position of any pits or shafts which it may be necessary to sink, whether for the sake of free ventilation, or for commencing and carrying on the excavation of the tunnel at several different places at the same time. Through these openings the stuff is to be hoisted up, and the water pumped out should any occur. The shafts being sunk to the requisite depth, which is ascertained from the levels which have been taken at the surface, a heading or small tunnel, at least sufficiently high and wide to allow the men to move freely in the work of excavation, is to be commenced just below the crown of the intended large one. Such smaller excavation is generally made very unshapely in the sides and roof, but ought to be nearly flat in the bottom. It is to be carried forward from one working shaft to another, as nearly as may be in a straight line, till a connection be formed between all the shafts and the ends of the tunnel. If, in the progress of the heading from one shaft to another, the air become so bad as to oblige the workmen to desist, an air shaft is to be immediately commenced from above, about five or six feet in diameter, and sunk vertically to the point at which the heading was left off. In excavating the tunnel of the Thames and Medway Canal, there were twelve working shafts; and, on account of the foulness of the air, it was besides necessary to sink eleven air-shafts. After the heading has been driven from one working-shaft to another, or a complete perforation obtained throughout the whole of the intended line, the roof of the tunnel is commenced, by an excavation in the form of a circular, an elliptic, or a parabolic arch. At this stage of the work the strength and quality of the roof are easily ascertained; and where weak and crumbling portions occur, a brick or stone arch must be formed for their support. The stuff is generally carried out by means of a railway. Some tunnels are formed in strata of such a texture as to require no building whatever, unless, perhaps, in fitting up a towing-path; whilst others are so very insecure that the construction of a complete lining of building must keep pace with the work of excavation. Some tunnels, again, are naturally water-tight, whilst others require a substantial lining of clay, and must be excavated of so much the larger dimensions as to have room for it.

**Inclined Planes.**

It is probable that the earliest mode of passing a boat from one level to another consisted in simply dragging it over the intervening space, whether that might be a natural rapid in a river, an obstructing rock, or a dam built across on purpose; and this last was generally in the form of a ridge, or double inclined plane. In a rapidly descending current it was necessary to have many such dams at short intervals, in order to obtain the requisite depth of water. In China these inclined planes have been long in use, especially in their smaller canals. Between the upper and lower levels of the water a double glacis of hewn stone is built, the principal slope of which extends from the bottom of the lower canal to the surface of the water in the upper canal, or a little above it, and there terminates in a large cross beam of wood, rounded off, and very smooth. From this beam another but shorter and steeper plane of stone descends to the bottom of the upper canal; and over these the boats are dragged, sometimes by simple manual power, and sometimes by the aid of capstans. It is not uncommon in China for a hundred men to be employed in drawing up a large vessel from the lower to the higher canal. Their strength is usually applied by means of levers turning capstans, which are placed on the abutments on each side of the glacis. A rope being passed round the stern of the vessel, has its ends attached to and wound round the capstans. In this way a vessel is more speedily raised into the upper canal than if locks had been employed; but it is effected by a prodigious exertion of human force, which, however, in China is always to be had at little cost, and is there preferred to any other. When a vessel is to be transferred from the upper to the lower canal, she is, as before, lifted over the cross beam, and then glides safely down by her own weight. To insure this, the head of the vessel is provided with a railing, which being covered with a strong matting at the time of the descent, not only breaks the fall, but prevents any water from flushing up over the deck. We here see human power sadly lavished away where a very different one might suffice. Horses, oxen, water-wheels, &c., are in some countries applied to turn machinery for the same purpose. To lessen the friction, long rollers are sometimes placed across the inclined planes, at short intervals from each other; but it is evident that, whether with or without rollers, boats which will bear to be dragged over any such structure must be excessively strong for their size. The long feeble boats which usually navigate canals would undoubtedly break into several lengths were they to be passed over the ridge. Sometimes the boats are placed upon a sort of cradle or hurdle, with or without wheels, and the whole dragged over; and sometimes the boats themselves are furnished with wheels, which only come into play in passing such planes.

There have been numerous other contrivances for transferring boats from one level to another, without any expenditure of water; and descriptions of the most of them will be found in some of the scientific journals, particularly in the Repertory of Arts, Nicholson's Journal, the Philosophical Magazine, and the Repertory of Patent Inventions. But these have generally been very unsuccessful, although for not a few of them patents have been obtained. One of the most recent patents is that of Mr Thomas Grahame, of which the specification is published in the Repertory of Patent Inventions for March 1837. By far the greater number of the schemes now alluded to would require an exertion of mechanical force which would either be more than sufficient to raise water to fill a common lock, or would be attended with greater expense. Some of them, it is true, might save a little time, but in general the case would be otherwise.

**Locks.**

Amongst the many approximations to the gates of a lock, the following rude one may be mentioned, especially as it is still used in various parts of England. A beam or sill is fixed across the bottom of the stream or canal; and directly over this, but at the water's surface, is placed a second but moveable beam. Against and behind these parallel beams a set of loose boards are placed upright and close together like a door, so as to obstruct the progress of the stream. When a boat is to pass, the boards are either removed singly, or, if they can be prevented from floating away, the upper beam is lifted or moved round, so as suddenly to let go the whole system, and thus afford a temporary increase of depth, to enable the boat to pass or repass the otherwise too shallow water. In China it is common to have a similar set of loose boards or planks, but placed horizontally across the stream; these being dropped one by one into grooves formed in the side walls, or in upright posts, from which the boards are to be singly removed in a similar manner. Such are the sluices or gates used on the Imperial Canal of China; for the emperor's boats or barges are far too large to be dragged over inclined planes. Machines of the same sort have also been used on the river navigations in Flanders. Since both the kinds of gates now described are supposed to be placed at the upper end of the fall or shoal over which they are temporarily to increase the depth of water, and since the boat is to pass through the gate, while the accumulated water rushes out with great force, it is evident that this must render it difficult for a boat to ascend the stream, and must accelerate it too much in descending. However, a method similar to this, at least in letting go a flash of water, has long been used in floating down rafts of timber over shallows and rapids in rivers, and is perhaps the best that could be contrived for the purpose. But for the navigation of boats there is a greatly preferable mode of using the same sorts of gates, so as to be free from the inconveniences above mentioned; which is to place the gate in moderately deep water at the lower end of the fall or shoal, and such that a boat may pass up through the gate before the water has been raised by it at all. The gate is then shut till the water rise sufficiently to enable the boat to ascend the fall or shoal, which it does in almost still water. These sorts of gates Lalande calls half-locks; and indeed it is supposed, with considerable probability, that the casual position of two of them near each other had given rise to the invention of the lock. For in that case it would soon be seen, that when the lower of these two gates was closed, and the water above it had risen to a sufficient height, such water would be nearly stagnant at the upper gate, and would afford an easy passage through it. If, therefore, the boat was ascending, the upper gate being next shut, the water above it would rise, and enable the boat to proceed a stage farther in its ascent.

However the real origin and early history of the modern Modern lock, like those of many other valuable inventions, are in-locks involved in obscurity, yet its nature and mode of operating will be readily understood by a reference to figs. 1 and 2, Plate CCCCLXXVIII., where AAAA are the walls of the lock chamber, which can be closed by the two single gates GG. The water in the part or reach of the canal which lies to the right of the lock is supposed to be higher than in that to the left. When, therefore, it is wished to pass a vessel upwards through the lock, she is first floated in at the lower gate, previously opened, as shown in fig. 1, and which is next to be shut. Water is then admitted through a valve, from the upper canal into the lock-chamber, till it has filled it up to the same level, and has of course raised the vessel along with it. The upper gate being next opened, the vessel quits the lock, and passes immediately into the higher part of the canal. This process is called locking up; and the reverse of it, or locking down, will obviously conduct a vessel down through the lock, which is to be emptied by another valve into the lower reach of the canal. For when the water in a lock is reduced to the lower level, it is usually said to be empty, although it has still the same depth of water as the lower canal.

In navigations where great differences of level are to be overcome, it is not unusual to have two or more locks following in such close succession that the lower gate, or pair of gates when they are double, of one lock, forms also the upper gate or upper pair of the next lock below it. This obviously tends greatly to lessen the cost of constructing them, and also requires fewer lock-keepers. It tends, besides, to lessen the time spent in the repeated stoppages and startings in the trackage of the boats; though it is rather blamed for expending somewhat more water than if the locks were scattered separately over a considerable extent.

It was not until artificial canals had become very general, that locks were brought to any thing like their present state of perfection; for the difficulty of procuring water had been but partially felt, as long as inland navigation was confined to a few rivers. But when the value of water for canals came to be properly appreciated, it was necessary to be careful of every resource, and to use it with the strictest economy. With this view the chamber, or the space between the upper and lower gates, instead of being made of an oval, a circular, or an octagonal figure, as in the locks on the earlier canals, was so much contracted as only to afford room for the vessels to pass through; to effect which, the sides were made vertical planes formed of wood, brick, or stone, instead of the sloping banks of earth or turf used in the older locks, and which required such a length of time to fill or empty them, and consumed a vast quantity of water besides. The lift of the lock, or the difference of level which it is made to overcome, is regulated by circumstances. It varies from one foot or less, up to sixteen or eighteen feet. Where the levels of the parts of a canal, or of the several reaches as they are sometimes called, differ greatly, and where water is plentiful, the locks are generally made with a greater lift than where the ground is more flat and the water scanty. For a given difference of level, locks generally consume more water as the lift of each is greater; but, on the other hand, they tend to save time. The chambers of narrow locks are generally from seventy to eighty feet long, and from seven to eight feet wide. Those of the Caledonian Canal are from 170 to 180 feet long, forty wide, and thirty deep; and still larger ones are used on the great ship canal from the Texel to Amsterdam; but locks are also made of every intermediate dimension.

A naturally hard bottom is the best foundation for the walls of locks; but where that does not occur, they are frequently built on a system of piles well driven and bound together; for the mode of preparing the foundation must be regulated by the nature of the ground. The sides are carried up sometimes in straight, sometimes in curved lines, and often reclining or battering outwards from the bottom. In this last case, too, the beds of the stone or brick-work are generally formed at right angles to the face of the wall, inclining from half an inch to an inch in the foot. Such battering, however, should only be used near the bottom; because, ceteris paribus, a lock the opposite sides of which are perfectly vertical and parallel planes, and which is of no greater width throughout than to admit the boats, must obviously consume the least water, and spend least time in passing a boat; a circumstance which ought always to outweigh any little saving of materials or expense which might be expected from a different form of construction. Curving the sides longitudinally, like crescents, can add nothing to the strength on the principle of the arch; because such a figure is at best an arch having nothing to abut against. The like may be said of dishing-carriage wheels, and of all curved structures which either have no abutments, or which are not equally pressed against all their abutments. At Agde, on the Languedoc Canal, a circular basin which unites three canals of different levels is used as a lock, and has long been extolled as the very perfection of lock-making; whereas it requires a needless length of time, and wastes an enormous quantity of water in passing a boat. If the foundation be clay or gravel, a wooden bottom is sometimes formed of cross sleepers planked longitudinally, upon which the side-walls are built with or without buttresses at the back, according to the quality of the side-banks. A flat segment or inverted arch of stone or brick is sometimes laid upon the wooden bottom, in order to distribute the weight more equably, and to prevent any partial settling or subsiding of the work; and the same method is observed between the buttresses along the outside of the chamber walls. In each wall, behind the hollow quoins, a recess is left sufficient for the gates to open back into, out of the way of the vessels. In the recesses belonging to the upper gates, a weir or overflow for the water is provided, four or five feet long, having a coping or sill of stone or brick, just the height at which the water is intended to stand in the upper reach of the canal; these are called the paddle-weirs or lock-weirs. A large flat stone is usually laid as a lintel over this opening, to complete the wall upon, and leaving a space of three or four inches in height for the egress of the surplus water. This cavity is conducted downward, diminishing in width and enlarging in depth, behind the walls of the lock, into the paddle-hole or culvert for filling the lock, if such be in use there. This water having got into the lock, makes its escape from it by a similar opening at the other end into the lower canal. In other cases a culvert is purposely continued behind the wall, so as to carry this surplus water quite past the lock to the lower canal. Sometimes an open channel, properly lined with stones or bricks, is made for it. But in many cases, where the surplus water would be of no use in the lower canal, it is allowed to escape over a waste weir, built on purpose in the side of the canal, into some river or brook which may be near. In order that any considerable quantity of water may be readily withdrawn from a canal when required, it is generally provided in various places with waste-gates or sluices in its sides, which can be drawn up either with a rack and pinion, a chain and roller, or a crow-bar, as circumstances may render most eligible. Sometimes pipes furnished with valves are placed in the bottom of the canal for withdrawing the water.

The frame of a lock-gate usually consists of two strong upright posts, connected by horizontal ribs; and the latter are closely covered with boards or planks caulked like a ship. The gate, again, generally turns horizontally on one of these uprights, which is called the heel-post or corn-post, whilst the opposite one is named the head-post or mitre-post. Large gates are frequently curved, so as, for greater strength, to present an arched or convex surface to the pressure of the water; and on this point there is an interesting article by Mr Barlow in the Transactions of Civil Engineers (vol. i.). It was usual to make all such gates of timber; but, on account of the difficulty of getting it at the time of sufficient size for those of the Caledonian Canal, the most of the gate-frames for it were made of cast iron, boards being still used for covering the ribs. Other locks have since been similarly constructed; and iron gates cast in one piece have been used on the Ellesmere Canal. But wooden gates are by some engineers preferred to those of cast iron, which are apt to corrode and get out of order, especially if exposed to the action of salt water. In England the cost of gates for large lock-chambers is nearly the same, whether they are made of wood or of iron. Some canal gates are made to rise and fall vertically, like those of ancient castles and temples, or, like our common windows, counterpoised by weights, which slide in grooves. The locks on the Shrewsbury Canal are not only closed by two gates of this sort, but can also be divided by others, so as to admit or contain one, three, or four boats at a time, without the loss of any more water than is just necessary to regulate the ascent or descent of the boat or boats that are then in the locks.

As it would on several accounts be inconvenient, and often impracticable, to open lock-gates against a strong pressure, they are either provided with smaller apertures furnished with valves, through which the locks are emptied or filled before opening the large gates themselves; or, instead of apertures in the gates, the water is passed through one or more culverts or pipes formed in the walls of the lock, these being in like manner furnished with sliding valves or paddles. The valves of lock-gates are generally opened and shut by a rack and pinion attached to the lever beams of the gates, and moving in vertical guides spiked fast to the lining of the gates. They are formed of wood, and placed near the middle of the gate at the bottom. A rack and pinion are likewise generally employed to open and shut the valves of culverts.

Sometimes the valve in a lock-gate is formed into a large lever, shaped like a rudder, which extends from near the bottom of the gate, and passes through a guide fixed on the side of the beam. One edge is hinged on a pivot about four feet above the bottom of the opening, the side-works against the lining of the gate, and the top is drawn backward and forward by means of a rack and pinion fixed on the lever beam. This is in some respects a convenient contrivance, being easily worked by the boatmen, without the awkward necessity of standing upon the lever beam.

Another method of constructing the valves, especially for large tide-locks, where the gates have no lever beams, but move upon rollers by means of a drag-chain, is to form two apertures above one another, each about one foot high by two feet wide, and to connect the two valve-covers by links at the same distance apart; so that a motion of one foot perpendicular, given by a coarsely threaded screw, fixed upon the head of a connecting rod, will open and shut four superficial feet of aperture through the gate.

But since all sliding valves are necessarily attended with much friction and wear, and it is likewise inconvenient to have any valve in the gates, we should think a greatly preferable method would be, to use a culvert departing perpendicularly in the bottom of the canal or of the lock-chamber, and to close it there with a horizontal lid or valve, hinged at one edge, and having a long arm or lever projecting from its opposite edge. In this simple construction, it is obvious that a mere rod or chain attached to the lever might have any required degree of power to raise the valve; which, on being let go, would readily, of its own accord, shut down out of the way. This method would scarcely either be attended with friction, or be subject to wear.

Many of the canals of England which have succeeded best are both narrow and shallow; and consequently their lock-chambers are narrow and long, particularly those of the Grand Trunk and Birmingham Canals. Fig. 1 and 2, Plate CCCLXXVIII., show one of these, which is seventy-five feet long and eight wide, with vertical and parallel sides AAAA, built of brick, four feet thick, and coped with stone. The gates G, G are single, hung in a stone quoin or coin, and they shut against a rebate of stone, which is lined on the corners with a cast-iron plate two inches thick and six broad, screwed fast to the coins. The gates are framed simply with square ribs, and a single lining of plank; they contain no valves, as the chambers are filled by side culverts c t e, formed through the wall, and entering in the recess left for the gate to fold back into. The valve v of these culverts is opened or shut by turning the handle w, which works a pinion and rack attached to a post about eight inches square. The gate is opened or shut by pushing round the long lever beam B, which is fixed along the top of the gate, and is purposely made very heavy to act as a counterpoise to the weight of the gate. The lower end of the coin-post, or principal upright post of the gate-frame, has a pivot which turns in a socket at the bottom; and near its upper end, at P, it is embraced by and turns in a collar held by the clamp a, which has two long diverging arms made fast in the top of the building.

The lock-chambers built by Brindley upon the Duke of Bridgewater's Canal at Runcorn, upwards of sixty-five years ago, are still in good order. They are formed with vertical sides of brick, coped with heavy stone clamped into the heart of the wall, and are sixty feet long by thirteen wide. The gates are double, and form, in meeting, a very acute-angled mitre. The valves or paddles are opened perpendicularly by a rack and pinion on the beam. There are two of these apertures in each gate, about twenty inches square. The hollow coins or grooves in contact with the gates are of timber, bolted and clamped into the brickwork.

3, 4, and 5, Plate CCCLXXVIII., represent one Tide-lock of the tide-locks of the Thames and Medway Canal. Its walls AAAA are of brick built upon piles with a wooden bottom, upon which is laid an inverted arch, the sides battering into the bottom curve from the water line. The gates G, G are double, and curved so as to form nearly a circular arch in meeting. Their frames are made of cast iron, and their coin and mitre posts are formed hollow like a pipe, with oblong openings in the sides for the workman to put in his hand with the bolts which are to fix the horizontal ribs. Formerly, when such posts had no openings in their sides, it was necessary that a boy should go inside with the bolts, like a sweep into a chimney. The ribs are about eighteen inches apart, an inch and a half thick, curved in plan, with a flange on each end, which is bolted into the coin and mitre posts. The ribs are covered with planks two inches thick, bolted to the ribs, and caulked in the joints like those of a ship. These gates are very heavy, but rest in a great measure upon rollers, which run on the curved tracks r, r, r, r when the gates are moved by the capstans C, C, C, C, and drag-chains winding round them, as seen in fig. 5, and denoted by the long, cross, dotted lines in fig. 3. These chains pass through holes in the walls O, O, as seen in fig. 5, where also the curve I denotes the inverted arch. This lock is filled and emptied through culverts, as described in the account of the single lock of the Birmingham Canal.

As the tide-water flows and rises above that within, it

---

There is little room to doubt that such would have been still more successful had they been of larger dimensions. However, the contrary error seems to have been committed in the too large dimensions of the Grand and Royal Canals of Ireland, and in the Caledonian Canal.

In some locks, instead of the drag-chain, a pinion is formed on the axle of the capstan, and works into a toothed rack attached by a joint to the gate. As the pinion and rack can work both ways, only one capstan is required for each gate; whereas the chains always need one capstan to open the gate and another to shut it. pushes open the gates G, G, and passes into the basin and canal; but this can also be stopped or prevented by shutting the gates g, g, which, opening outward, cannot give way to external pressure. The lock-chamber is 130 feet long within the outer gates, and thirty wide. It is about ten feet deeper than the canal, and eight wider than the tunnel, which is only twenty-two feet; so that much larger vessels may come into the basin, whose bottom is even with that of the lock, than those which can get through the canal. By these means, too, boats drawing almost eight feet, the ordinary depth of water in the canal, may pass through the lock when the tide-water without is ten feet lower than in the canal.

This lock exhibits one feature which, though common a century ago, we should not have expected in a first-rate lock made in the nineteenth century; we mean the curvature of the side walls, which contributes rather to weaken the structure, because, instead of these curved sides acting as arches having something immoveable to abut against, their only tendency in the circumstances is to transfer the lateral pressure from the middle of the walls, where the stress is least, to the very parts on which the gates are hung, and which, of course, already sustain the greatest strain, and therefore have more need of being relieved or assisted, than thus burdened with any such unnecessary or additional strain.

When a boat is to be raised through a given height, there is not necessarily any difference in the expense of water, whether the ascent be gained by one previously empty lock, embracing the whole lift, or by ever so many sharing it; for since the boat on ascending leaves all the locks full, there must at least be as much water used as would fill up one deep lock from the lower to the higher level, and which ought just to fill over so many shallow ones. However, when the locks have been previously full, the water of one only need be expended, and therefore the less the lift of each, the less will be the expense of water. On the other hand, it is obvious that many small lifts unavoidably put off much time. Again, when a boat is to have a given descent, this may be effected with as much less expense of water as the number of locks, if previously empty, is greater; because, whatever water suffices for one of a series of equal locks, may successively serve each of the rest during the descent. When the locks have been previously full, the whole of them are emptied by the descent of a boat, whether they are many or few. However, there is this difference between an ascent and a descent: A boat in ascending lets down or consumes twice the weight in water of itself and cargo more than it does in descending; because, on entering the empty lock, the boat which is about to ascend expels as much water into the lower reach of the canal as equals the weight of itself and cargo, whereas a boat about to descend expels from the full lock an equal weight of water into the upper reach of the canal. The former is therefore lost, whilst the latter is saved.

The failure of the schemes hitherto projected for remedying the defects of the common lock are ascribed by M. Girard to the impossibility of resolving the problem completely, without an unnecessary expenditure of mechanical force; and he therefore reduces the maximum effect of the common lock to questions of the comparative time and economy required by boats in passing insulated locks, and in passing connected systems of locks. But he does not, says Mr Rennie, consider the stoppage and the loss of time attending the repeated changes in the force of trackage required by the isolated system. The value of the water lost can only be contrasted with the value of time under certain circumstances; but the question had already been discussed by Gauthy and others with reference to the locks of the Canals of Briare and Languedoc.

**Economy of Water.**

There have been numerous expedients for more effectually economising the water of canals. By making the lock double, that is, placing two equal locks on the same level in the breadth of the canal, a much smaller quantity of water will generally suffice. For since a boat on descending must enter a full lock and leave it empty, whereas an ascending boat must enter an empty lock and leave it full, it would obviously be a saving of water could the full lock, by which a boat had ascended, be reserved for the next boat which should descend, and vice versa with the empty one; though it is evident, that when several boats pass together in the same direction, this can only be partially done. But when the one lock is full and the other already empty, and we wish to let down a boat through the former one, half the water might always be let through a sluice into the empty lock, instead of letting the whole go to waste in the lower canal; and in like manner, when we wish to raise a boat through the empty lock, half the water may be obtained from the full one. By putting more than two locks in the breadth of the canal, still less water would sometimes suffice; but the increased cost puts this out of the question.

A different method of saving water is by means of side-side-ponds, into which the water is partly withdrawn from a full pond-lock, and reserved for farther use. Sometimes a single side-pond is employed, and sometimes two or more, being all upon different levels. A single pond, no matter how extensive, cannot, in the usual way in which it is employed, save quite half the lockful of water, two ponds cannot save quite two thirds, nor can three save three fourths, &c. But it is most common to employ two ponds, each having the same horizontal area as the lock has, and being made to receive one fourth its fill of water. The one of these ponds has its bottom at half the height or lift of the lock, so that when a valve is opened into it from the full lock, this pond receives one fourth of its contents. This valve is now shut, and another valve opened between the lock and the second pond, which, in its turn, receives another fourth of the water, because its bottom is at one fourth the height or lift of the lock. The second valve is now shut; and the remaining half-full of water in the lock is let go into the lower canal in the usual way. When the lock is to be filled again, the lower pond is first run into it and closed, and then the higher one, which together make up one half of what will fill the lock, and which has been saved by means of the ponds.

A great improvement on side-ponds has been proposed by Mr Field (Transactions of Civil Engineers, vol. i. p. improve-61), which is to apply to them the principle of the pendulum, or rather of water vibrating in an inverted syphon, viz. that it would rise to the same height in the one leg as that from which it has fallen in the other, were it not for friction or other resistance. Mr Field's method is to connect a lock with a side-pond by means of a long pipe or culvert, in such a manner, that when the water in the lock is allowed suddenly to run into the empty pond, it may rise in the latter nearly to the level from which it had fallen in the former; and at the moment this occurs, the valve or sluice in the culvert is to be shut. The same thing should obviously take place when the water is to be restored to the empty lock, excepting that, whatever may have been

---

1 Reports of the British Association for 1834, p. 459. the loss of water in the former case, the total loss will now be doubled; but this additional loss would be avoided by using a second lock alongside of the other, instead of a pond, as no restoration would be required.

On one point we beg to differ materially from Mr Field. In all the five different forms in which he has illustrated his method, he assumes it as absolutely necessary that the long culvert should always have two valves, one at each end; and in order to get these two valves near each other, he proposes to bend round the culvert in a spiral or circular form. Now, with all deference, we presume, that if the culvert be kept as low down as it ought to be on several accounts, any more than one valve will not only be troublesome and expensive, but occasion a needless obstruction to the free motion of the water. Indeed, to avoid giving a great and sudden lateral shock to any boat or vessel whilst in the lock, it would be proper that the water should enter or depart perpendicularly in the middle of the bottom of the lock. In that case it would not be very material in what part of the culvert the valve was situated, except for the greatest convenience. It would perhaps be an improvement to give the culvert very wide spreading mouths or ends. If, however, Mr Field's ingenious scheme should save nine tenths of the water, as he expects it to do, it would have the farther advantage, that the gates of such locks could generally be opened without their needing to have any valves or paddles to be previously opened, either in them or in the walls. Mr Field makes his method to depend on the principle of Montgolfier's ram, a principle, we beg to observe, which had been discovered, applied, and published by Whitehurst, long before Montgolfier's time; but it is much more elementary and simple, we presume, to refer, as we have done, so much of Mr Field's scheme as has now been described, to the undulations of water in a syphon.

Where canals are all on one level, and have either no locks at all, or at their extremities only, there is seldom much difficulty in supplying them with water; though in certain cases canals of this sort may communicate with some very muddy river, whose waters, if admitted, would soon silt them up with mud. In such cases it has been recommended to exclude the muddy water, and, if nothing better could be done, to supply the canals with clean water, raised by a steam-engine. This method has been followed in the case of the West India docks on the Thames, where the foul water of that river, after having stood in a basin till it has deposited its mud, is pumped up into the docks by a steam-engine. But where a canal is to form a communication between separate valleys or basins of a country, and where a double lockage is unavoidable, the summit-level which divides the rise and fall is generally too elevated to permit a regular supply of water being drawn directly from the streams on either side. In such cases it becomes necessary to collect the flood waters of the adjacent higher grounds into proper reservoirs, to be used as circumstances may require. Some canals are provided with very large receptacles for the flood-waters. That of Languedoc has one of 595 acres; and one belonging to the Trent and Mersey Canal covers 160 acres. But cases occur in which no such supply can be obtained, and where, of course, it is necessary either to raise water by steam-engines, or to employ inclined planes or machinery to pass the vessels, or at least their cargoes, from one level to another.

**RIVERS.**

Engineers are generally agreed that side artificial canals are eventually more judicious than the attempts to dredge or to deepen channels in the beds of the streams themselves; and that, for the purposes of navigation, rapid rivers are only useful to supply canals with water. On this account, locks are rarely constructed in the beds of rapid rivers. It is more usual to apply them to side-cuts or to a lateral canal, formed for the purposes of the navigation, and to leave the river course for the passage of the floods or other surplus water. A quick bend of the river is generally chosen for being crossed by a side-cut; and to keep up the water to a sufficient height for navigation in the upper part of the river, a dam or weir is thrown across the old river course, at or rather a little below the upper point at which the artificial cut joins it. The lock is then built at the most convenient part of the cut, generally near the upper end; and its fall or lift is made equal to the difference in the levels of the water at the top of the dam or weir, and in that at the lower end of the cut. But it may happen, that, owing to some rock or other natural obstruction in the river, no artificial dam will be required; and, on the other hand, it is probable that the fall of the river may be so great that several locks will be required in the same cut.

Of the impropriety of placing locks in a rapid current, a remarkable instance may be mentioned in the case of the locks which Polhem, a Swedish engineer, fearlessly attempted, in 1755, to place in the cataracts of Trollhaetta, in the river Gothia, but which were wholly swept away by a flood, after they had been considerably advanced, and vast sums expended upon them.

In estimating the propriety of deepening shallows in any river, it must be of importance to take into consideration the nature of the shoals. If they have been created by deposits collected by the action of the current, it may be inferred that the same process will continually tend to the same results, and that any efforts to preserve the channel clear will require to be perpetual and laborious; but if the obstructions have been artificially made, or consist of a natural and solid substratum, it may be reasonable to presume that the excavations once made will either be permanent, or, at all events, be easily maintained.

Regarding the main question, whether the free and natural flow of the floods is to be arrested by locks, dams, and other works, the principles which have guided the operations of different engineers have been various and contradictory; but, in general, the practice has been to confine the freshes by artificial works, as in the Clyde, Witham, and other rivers, and to preserve the basins, or other receptacles for tidal waters, to their full extent. A contrary proceeding has tended to ruin many rivers and estuaries, and consequently to impede the drainage and navigation in a great degree, and to occasion the destruction of several harbours, such as those of the Dee and Rye. The effects of embankments in Plymouth and Portsmouth harbours, and particularly in the estuary of the Mersey, one third of the ancient capacity of which has been filled up by encroachments, have materially diminished the depths of the sea-channels, and a consequent deterioration of the harbours has been the result.

Where the navigation of a river is impeded by its waters being too much spread, or occupying too wide a channel, this may be remedied by contracting it by embankments, which will have the effect of increasing the depth of the stream, whether it scour out the bottom so as to lower it or not. Such is the usual mode of forming inland navigations in China. It has the advantage of being more speedy than passing through locks, and, indeed, rather too speedy to be safe for vessels in descending. A great power is, in some such cases, required to make a vessel ascend through the contraction. This is accomplished in a variety of ways; often by men aided by capstans; in other cases by machinery, such as a mill being at hand, which may be employed for towing up the vessel, while its weir or dam may, besides, be useful in prolonging the navigation of the river considerably farther up.

A splendid example of some of the more recent operations in the management of rivers is to be found in those of M. de Fontaine on the Rhine. Near Emmerik the Waal branches off from the Rhine, so as to form two nearly equal rivers, each of which has its bed almost as large as that of the whole river; and when the waters rise, they are at an equal height in both. The Rhine divides itself again towards Arnhem to form the Issel, which has nearly the same section as the Rhine. The first division of all the waters of this river was begun under the Roman generals Drusus and Corbulo; and many subdivisions were made in subsequent ages. But such a multiplicity of channels, although productive of advantages to Holland, led to many fatal consequences. The waters being so much subdivided, lost the rapidity and strength necessary to push forward the alluvial matter, which being therefore deposited, occasioned a continual rising of the bottom, rendered the drainage of the adjacent lands more difficult, increased the expense of the embankments, and augmented the damages over the extensive lands when the dikes happened to break. The irregularity of the course of the Rhine, and the ravages which it constantly committed on its shores, particularly those of Alsace, one of the most fertile provinces of France, rendered the construction of defensive works imperative; and in 1820 M. de Fontaine was selected to perform this important task. The part of the Rhine to which he principally directed his attention is comprised between Basle and Neuburg, that being the political limit between France and the German states. In this part, the bed of the river is situated in the alluvium which forms the bottom of the valley; and through this the Rhine forces its way by many channels, forming, in its passage, islands and sand-banks, which render its motions very irregular both in times of high and low water. Amongst the different streams there is generally one more considerable than the others, and which forms the navigable channel. These branches are annually diminished by artificial works, and probably in a few years the whole of the waters of the Rhine will be forced into one channel, which may then be expected to become so much deeper, and freer from obstructions, as to be far more fit for navigation.

To enable vessels to ascend a rapid in a river, a powerful though rather tedious method, called warping, has been long in use. This consists in attaching or making fast one end of a rope somewhere up the rapid, and then winding up the other by means of a windlass or capstan on board, till the vessel ascends against the stream. Sometimes a tug-boat in constant attendance at the rapid is provided with two paddle-wheels, one on each side, which, turning by the force of the stream, wind up the rope on their axle, and enable the tug itself not only to ascend the torrent, but also to draw up other vessels after it. This method is probably at least a century old, being described in the Machines Approvées par l'Académie des Sciences; but within the last twenty years it has been repeatedly announced as a wonderful discovery just made, sometimes here and sometimes in America. This shows the importance of diffusing knowledge, to save ingenious men from useless wasting their time in re-inventing what is already well known. Sometimes a paddle-wheel stationed somewhere up the rapid winds up the rope, and draws the vessel to it, which we should think by much the better method. Where the navigation of a river is incumbered by shifting mud or sand, the force of the current is sometimes employed, particularly in France, to urge forward a plank held on edge across the stream, so as to make it clear the way like a snow-plough for a fleet of boats, &c. which are to follow. But it is more systematic to have a boat provided with flaps or wings for cleaning a river.

BRIDGES.

Where canals or rivers are navigated only by such boats as have neither masts nor rigging, the bridges over these waters are, for the most part, fixed, and have scarcely any thing peculiar in them on account of the navigation, except that the arch may rise a little higher, and have a towing-path under it, as shown at B, fig. 8, Plate CCCLXXIX. But a moveable bridge is always employed where a fixed one would occasion too great a rise in a road, or where the arch cannot be elevated sufficiently to clear the masts of vessels. There are several sorts of moveable bridges.

The draw or lift-bridge AA, fig. 8, is one which is Draw-fastened with a joint or hinges at one end, so that the other bridge end may be lifted or let down by some easy artifice. Formerly this sort of bridge was lifted and suspended by chains and levers working in a huge wooden frame, which was often of great height, and usually painted in gaudy colours, to the great terror of such horses and other animals as were unaccustomed thereto. Some of these were long to be seen on the Forth and Clyde Canal. But such bridges are now generally lifted, without chains or levers, by turning a pinion which works into a toothed-rack fixed upon the bridge; or, if the bridge is large, it has two of these racks and pinions. This simplification of drawbridges is said to have originated with M. Perronet in France. For small canals a drawbridge consists of one leaf or frame only; but for entrances to docks and harbours, and for large canals, such as that of the Forth and Clyde, it is made in two halves, which meet in the middle when they are shut or let down. Such bridges, however, have been found inconvenient in practice, from their being apt to catch the yards and rigging of vessels in passing through them.

This inconvenience has given rise to a different form Swing or of moveable bridge, which, instead of lifting, like the former, round a horizontal axis, swings or turns horizontally, as it were, round a vertical axis; but the weight of this bridge is not supported on the centre or axis, but rests and is poised upon a circular series of balls or rollers surrounding the centre of motion. Some of the earliest of these bridges were principally made of wood, and for small canals consisted of a single leaf only; but they are now commonly made of cast iron, and, when large, are double. Fig. 1 shows an elevation, and fig. 2 a plan, of a double bridge of this sort, by the late Mr Ralph Walker, where AA is the line of the roadway, RR the rollers and lower ring, shown separately in fig. 6, with the outer ring to which they are attached. The upper ring is seen in fig. 4. Fig. 5 is a vertical section of the bridge through the centre of the rings, supposing the bridge and building to be laid on their side, and the section to be made across the roadway. In fig. 7, F is a vertical section of the abutment, while E is the upper side of the cross for the pivot, round which either half of the bridge turns. Fig. 3 shows a section of the part of the bridge to which is attached the pinion, which, by working in the fixed segment by means of the handle H, turns either half of the bridge quite out of the way of vessels passing along the river or canal, and also brings it back or shuts it again. GG are holes for putting in pins for locking the bridge. When the bridge is shut, three of the five ribs bear at right angles on the abutments; the other two are secured upon the upper circles, and at GG. We should think that a far

---

1 Fontaine, Des Travaux du Fleuve du Rhin, 1833; and Mr Rennie's Report on Hydraulics.