The art of glass-making was introduced into Scotland in the reign of James VI. An exclusive right to manufacture it within the kingdom, for the space of thirty years, was granted by that monarch, to Lord George Murray, in the year 1610. This right his lordship transferred in 1627, for a considerable sum, to Thomas Robinson, merchant-tailor in London, who again disposed of it for £500, to Sir Robert Mansell, vice-admiral of England. The first manufactory of glass in Scotland, an extremely fine one, was established at Wemyss in Fife. Regular works were afterwards commenced at Prestonpans, Leith, and Dumbarton. Crown-glass is now manufactured at Harrington, St Helens, Eccleston, Old Swan, and Newton, Lancashire; at Birmingham, Hunslet near Leeds, and Bristol. It is also manufactured of excellent quality on the Tyne and Wear. Great improvements have recently been made in the manufacture of crown-glass; and we believe this article, as made in England, is superior in quality to that of any other nation.

There is good reason for supposing that the art of staining or painting glass is coeval with the art of making glass itself; since, as has been noticed above, it is difficult to make it without colour. The possibility of subjecting this art to the will of the manufacturer must have very obviously presented itself; although it certainly requires much art and chemical knowledge to produce perfect specimens of this description of manufacture. This perfection seems, however, to have been attained at a very early period. It is certain that the art was known in Egypt at least 3000 years ago. We have already mentioned the beautiful imitations of precious stones, found adorning tummies which are known to have existed for that time. We meet with frequent mention of specimens of Eastern workmanship of consummate beauty, upon which great value was placed. The Emperor Hadrian, whilst at Alexandria, was presented by an Egyptian priest, with two glass cups, which sparkled with colours of every kind, and which had been used in the service of the temple. These were prized so highly that he ordered that they should be produced only on festivals and great solemnities. The works of Caylus and Winkelmann furnish some striking instances of ancient skill in the formation of pictures by means of delicate glass fibres of various hues, which, after being fitted together with the utmost nicety, were conglomerated by fusion into a solid mass. The art of combining the various colours, so as to produce pictures, such as is now practised, is comparatively of recent date. The earliest specimens of this kind of work discover a factitious joining of different pieces of glass, differently tinged, and so arranged as, by a species of mosaic work, to produce the fire or figures wanted. The various pieces are held together generally by a vein of lead, run upon the back of the picture, precisely at their junction.

But modern ingenuity has superseded this clumsy experiment; and every colour used in painting can now be introduced into one entire sheet. For a long period the pictorial glass used in cathedrals was merely painted on the surface, the art of incorporating the colours with the glass by fusion, the method now practised, being unknown till the beginning of the fifteenth century. This great improvement is ascribed to a painter of Marseilles, who went to Rome during the pontificate of Julius II.; but his discovery went no further than the producing of different colours on different pieces of glass, and having them afterwards united in the old fashion. This art was, at a later period, greatly improved by Albert Durer and Lucas of Leyden, the latter of whom brought it nearly to the state in which it is now practised.

The first painted glass executed in England was in the time of King John; previously to this, all stained or painted glass was imported from Italy. The next notice of it occurs in the reign of Henry III. The treasurer of that monarch orders that there be painted, on three glass windows in the chapel of St John, a little Virgin Mary holding the child, and the Trinity, and Saint John the Apostle. Some time after, he issues another mandate for two painted windows in the hall.

Even at this early period, however, England boasted of eminent native artists in glass painting, amongst the first of whom was John Thornton, glazier of Coventry. This person was employed, in the time of Henry IV., by the dean and chapter of York cathedral, to paint the eastern window of that splendid edifice; and for the beautiful and masterly workmanship which he exhibited in this specimen of his skill, he received four shillings per week of regular wages. He was bound to finish the work in less than three years, and to receive, over and above the weekly allowance, one hundred shillings for each year; and if the work was done to the satisfaction of his employers, he was to receive, on its completion, a further sum of L10.

From this period downwards there have been many skilful native artists, although the Reformation greatly impeded the progress of the art, by banishing the ungodly ostentation of ornamented windows from churches; indeed, so serious was this interruption, that the art had nearly altogether disappeared in the time of Elizabeth. Amongst the most eminent glass painters who first appeared upon the revival of the art, were Isaac Oliver, born in 1616, and William Price, who lived about the close of the seventeenth century. This last person was for many years the only glass painter in England. He is said to have discovered, what is to this day a desideratum in the art of glass staining, the secret of producing a rich, clear, bright, and transparent red, the most difficult to strike, and the most expensive of all the colours employed in glass painting. But Price having died soon after making this discovery, his secret died with him. This artist was succeeded by a person at Birmingham, who, in 1757, fitted up a window for Lord Lyttleton, in the church of Hajely. To him succeeded one Peckitt of York, who attained considerable eminence in the art.

During all this time, however, and indeed until a comparatively recent date, painted glass was regarded as too costly and too magnificent an article to be otherwise employed than in decorating religious edifices or the palaces of nobles; and even in the latter case it was but sparingly used. Modern improvement has now placed this beautiful ornament within the reach of very ordinary circumstances; and, when this is considered, it must excite a strong feeling of surprise to find how little so elegant a luxury is even yet in demand. The art of staining glass is now practised with very great success. The colours of modern artists, we venture to allege, notwithstanding what is often urged to the contrary, equal in variety and richness those of the ancients; and, with the superior knowledge which we now possess of the principles of draw- ing, and of bringing several colours together on a single sheet, encouragement alone is wanting to attract artists of talent and inventive genius to the pursuit of the art, and to carry it to a greater height of excellence than it has ever reached in the hands of their predecessors.

**MANUFACTURE OF CROWN-GLASS.**

In order to secure success to his operations, the glass manufacturer must bestow the utmost care upon the erection of his furnaces. They must be well and substantially built, of the best materials, of the most approved construction, and under the direction of a builder of tried skill and extensive experience. A false economy in these respects cannot fail of leading to the most ruinous results.

Crown-glass is the best kind of glass now employed in the glazing of windows, and is so called to distinguish it from the common, broad, or spread glass, which was in use before the introduction of crown-glass, but which, on account of its inferior quality, is now rarely used. In the manufacture of crown-glass the following furnaces and arches are required, viz. calcar arch, main furnace, bottoming hole, flashing furnace, nose hole, and annealing kiln.

*A Calcar Arch* for burning frit is a common reverberatory furnace, and is about ten feet long, seven feet wide, and two feet high. A building ground plan and elevation of one is shown in Plate CCLXVI. figs. 4 and 5. The crown and sides are built of fire-brick, and the other parts of common brick. The bottom should be carefully joined and cemented, as the salt is apt to ooze through it.

*The Main or Glass-making Furnace* is an oblong square, built in the centre of a brick cone, large enough to contain within it two or three pots at each side of the grate-room, which is either divided, as shown in the plan, or runs the whole length of the furnace, as the manufacturer likes. Plate CCLXVI. fig. 3 is a ground plan, fig. 2 is an end elevation, and fig. 1 a front elevation, of a six-pot furnace. 1, 2, 3, fig. 1, are the working holes for the purpose of ventilation, for putting in the materials, and for taking out the metal to be wrought. 4, 5, 6, 7 are pipe holes for warming the pipes before beginning to work with them. 8, 9, 10 are foot-holes for mending the pots and sieges. 11 is a bar of iron for binding the furnace, and keeping it from swelling.

The arch, as shown in fig. 2, is of an elliptic form. A barrel arch, that is, an arch shaped like the half of a barrel cut longwise through the centre, is sometimes used. But this soon gives way when used in the manufacture of crown-glass, although it does very well in the clay-furnace for bottle-houses.

The best stone for building furnaces is fire stone from Coxgreen, in the neighbourhood of Newcastle. Its quality is a close *gree*, and it contains a greater quantity of talc than the common fire stone, which seems to be the chief reason of its resisting the fire better. The great danger in building furnaces is, lest the cement at the top should give way with the excessive heat, and, by dropping into the pots, spoil the metal. The top should therefore be built with stones only, as loose as they can hold together after the centres are removed, and without any cement whatever. The stones expand and come quite close together when annealing; an operation which takes eight to fourteen days at most. There is thus less risk of anything dropping from the roof of the furnace.

The inside of the square of the furnace is built either of Stourbridge fire-clay annealed, or the Newcastle fire-stone, to the thickness of sixteen inches. The outside is built of common brick about nine inches in thickness.

The furnace is thrown over an ash-pit, or cave as it is called, which admits the atmospheric air, and promotes the combustion of the furnace. This cave is built of stone until it comes beneath the grate-room, when it is formed of fire brick. The abutments are useful for binding and keeping the furnace together, and are built of masonry. The furnaces are stoutly clasped with iron all round, to keep them tight. In four-pot furnaces this is unnecessary, provided there be four good abutments.

*Bottoming Hole.* Plate CCLXVII. figs. 3 and 4. Elevation and ground plan. The interior is of common fire-brick, the mouth either of common fire-brick or Stourbridge clay, and the outside entirely of common brick.

*Flashing Furnace.* Figs. 5 and 7. Elevation and ground plan. The outside is built of common brick, the inside of fire-brick, and the mouth or nose of Stourbridge fire-clay.

*Nose Hole.* Fig. 6. Elevation. This is a small aperture off the flashing furnace, and of the same materials. Fig. 7, ground plan.

*Annealing Kiln.* Figs. 8 and 9. It is built of common brick, except around the grate-room, where fire-brick is used.

The materials of which crown-glass is usually composed are kelp and fine white sand. Pearl ashes, or certain other alkalis, sometimes supply the place of the former of these substances. The quality of kelp is extremely various. That from Orkney is superior to what is made in Ireland, the Hebrides, or the lower parts of Scotland. It is found to contain less alkali, and to produce glass of a better colour. For the glass-maker's purposes the kelp of the Orkneys is decidedly the best. It is freer from sulphur than the others, the presence of which makes the glass green, crude, and fretful. The following is the course pursued in the preparation of kelp. The fuci are cut from the rocks in the months of May, June, and July. They are then brought to the shore, and, after being spread out and dried, are thrown into a pit lined with stones, in which a large fire of peat has been previously kindled. On this fire the weed is heaped from time to time, until a large mass is accumulated, and the whole is reduced to a state of fusion. It is then well mixed and levelled, and allowed to cool. When sufficiently cold, it is taken from the pit, and broken into portable masses, for the convenience of transportation. To prevent the dissipation of the alkali, a thing very apt to occur, the greatest care is necessary in every part of this process: in the gathering and drying, as well as in the burning of the fuci; in the treatment of the mass whilst in a state of fusion; and in its exposure to the atmosphere during these operations. Kelp burners are but too frequently guilty of carelessness in this respect. In some places they burn the fuci in pits which are not lined with stones, and, of consequence, sand and earthy substances mingle with the fused mass. It is no uncommon thing for the makers to increase the weight of kelp intentionally, foolishly thinking to procure a high-

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1 Some eminent chemists assert that, although the usual quantity of kelp be added in the manufacture of glass, the weight of the glass produced is nothing more than the original weight of the sand. But this is not the case with the Orkney kelp, for though it has less alkali, it contains more insoluble matter than the West Highland kelp, and of course produces a larger quantity of glass. The West Highland yields glass of very inferior colour to that procured by the use of Orkney kelp.

2 The best mode of preparing kelp, as invented by Colonel Fullarton, is by burning it in a reverberatory furnace, and throwing it down in the form of cakes, in the same manner as frit, which we shall afterwards have occasion to describe. When so prepared, it is more fit for the glass manufacturer, being free of extraneous matter. This method is now employed by extensive makers of kelp in Ireland. This process is from twenty to twenty-four hours. It can also be blown to a thinner and finer substance, and is thus liable to a less duty. When the sand and kelp are thoroughly mixed, the compost is put into a calcining arch or reverberatory furnace, where it is subjected to a heat so strong as to reduce it to a semifluid state. Whilst in this state, it is stirred without intermission, to prevent the formation of knots containing more sand than the rest of the batch, an effect resulting from the dissipation of the alkali by excess of heat. The process of calcining requires more or less time according to the varying properties of the ingredients composing the batch. From three to four hours is the time usually occupied by each batch. The frit, as the substance is now called, is taken from the furnace, spread upon a plate of iron whilst yet hot, and, before it becomes quite cold, divided into large cakes. In the opinion of many, it cannot be too old for use; as when new the glass made from it is full of what are called seeds. It is commonly kept about six months by opulent manufacturers. The last operation consists in throwing the frit into the melting pots, which are of the form represented in Plate CCLXVIII., fig. 2.

To prevent stones or clay from the furnace falling into the pot, those used in making flint-glass are always covered in on the top; and the same thing has been tried in crown pots, made with two openings, one in the front and one in the back, the back one to be plugged up when beginning to work from the front of the pot. This method succeeded very well, but was abandoned from the length of time it required; a circumstance which more than counterbalanced its advantages.

These pots or crucibles are made of the finest clay. That from Stourbridge in Worcestershire is considered the best. Great care is requisite in the selection, and in cleansing it from extraneous particles, the presence of which, even in the smallest degree, will injure the pot. A fine powder procured by grinding old crucibles is generally mixed, in a proportion seldom larger than a fourth, with what is termed the virgin clay. This mixture dries more rapidly, contracts less while drying, and presents a firmer resistance to the action of the fire and alkali used in the composition of glass than the mere unmixed clay. These ingredients having been mixed, they are wrought into a paste in a large trough, and carried to the pot loft, covered in such a way as to exclude dust and other minute particles. Here a workman kneads this paste by tramping it with his naked feet, turning it from time to time until it becomes as tough as putty. It is then made into rolls, and wrought, layer upon layer, into a solid and compact body, every care being taken to keep it free of vacuities, as latent air would, by its expansion in the furnace, cause an immediate rupture of the pots.

After pots are made, very great care is necessary to bring them to the proper state of dryness before taking them to the annealing or pot arch. In drying they commonly shrink about two inches in the circumference. When pots are made during summer, the natural temperature is sufficient. In winter they are kept in a temperature of from fifty to fifty-five degrees Fahrenheit. They remain in the room where they are made for a period varying from nine to twelve months. Being afterwards removed to another apartment, where the heat is from eighty to ninety degrees Fahrenheit, they are kept there for about four weeks. They are then removed for four or five days, more or less, according to their previous state of dryness, to the annealing arch (of which figs. 1 and 2, Plate CCLXVII., is an elevation and ground plan), which is gradually and cautiously heated up till it reaches the temperature of the working furnace, whither, after being sufficiently annealed, they are carried as quickly as possible. Pots last upon an average from eight to ten weeks. Their value is usually estimated To the frit thrown into these pots there is added a proportion, about an eighth, of cullet or broken crown-glass. After this has been done, the furnace is raised to the highest possible degree of heat. The pots are filled every third hour or so, according as the frit melts, till they are completely full. The intensity of the heat is then increased, if possible, till the metal, as it is now called, is reduced to fine liquid glass, which is then ready for the operations of the workman. From twenty-four to thirty hours in all are required for this process, which is called founding.

The furnace is slackened for about two hours, and the metal being now in a workable state, the first operator who approaches the furnace in which the pot of liquid glass is placed is the skinner, who skims off all crude or extraneous substances from the surface of the metal. Next follows the gatherer, who is provided with an iron pipe or tube, six or seven feet in length, and of this shape.

Having previously heated that end of the tube which takes up the glass, he dips it into the pot of metal; and by turning it gently round, gathers about one and a half pound of liquid glass on the end of it. Having allowed this to cool for a little, he again dips it into the pot, and gathers an additional quantity, of from two and a half to three pounds. This is also permitted to cool as before, when the operation of dipping is again repeated, and a sufficient quantity of metal, from nine to ten pounds weight, is gathered, to form what is technically called a table or sheet of glass. The rod, thus loaded, is held for a few seconds in a perpendicular position, that the metal may distribute itself equally on all sides, and that it may, by its own weight, be lengthened out beyond the rod. The operator then moulds the metal into a regular form, by rolling it on a smooth iron plate, called the "marver," a term corrupted from the French word marbre.

He then blows strongly through the tube, when his breath penetrating the red-hot mass of glass, causes it to swell out into a hollow pear-shaped vessel, thus:

The tube with the elongated sphere of glass at the end of it is then handed to the blower, who heats it a second and third time at the furnace, pressing the end, between each blowing, against the bullion bar, so called from the part thus pressed forming the centre of the sheet or bull's eye, thus:

By the dexterous management of this operation, the glass is brought into a somewhat spherical form.

The blower heats a third time at the bottoming hole, and blows the metal into a full-sized globe thus:

When this part of the process has been completed, and the glass has been allowed to cool a little, it is rested on the casher box, and an iron rod, called a "pontil" or punty rod, on which a little hot metal has been previously gathered, is applied to the flattened side, exactly opposite the tube, which is detached by touching it with a piece of iron, dipped beforehand in cold water, leaving a circular hole in the glass of about two inches diameter. The operation of attaching the punty is shown by the following plate.

Taking hold of the punty rod, the workman presents the glass to another part of the furnace called the "nose hole."

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1. The sandier or glass gall is removed while the furnace is at its extreme degree of heat. 2. A piece of wood about eleven inches long by seven broad, with a hole three inches by one inch, forms an excellent protection to the eyes from the heat to which they are exposed when examining the metal in the pots. where the aperture made by its separation from the tube is not presented and kept until it has become sufficiently dense to fit it for the operation of the flashing furnace. Whilst here, it is turned dexterously round, slowly at first, and afterwards with increasing rapidity; and the glass yielding to the centrifugal force, the aperture just mentioned becomes enlarged.

The workman, taking great care to preserve, by a regular motion, the circular figure of the glass, proceeds to whirl it round with increasing velocity, until the aperture suddenly flies open with a loud ruffling noise, which has been aptly compared to the unfurling of a flag in a strong breeze; and the glass becomes a circular plane or sheet, of from four to five and a half feet diameter, of equal thickness throughout, except at the point called the bullion or bull's eye, where it is attached to the iron rod. The following figure will give some idea of this very beautiful part of the process.

The sheet of glass, now fully expanded, is moved round with a moderate velocity until it is sufficiently cool to retain its form. It is carried to the mouth of the kiln or annealing arch, where it is rested on a bed of sand, and detached from the punty rod by a shears. The sheet or table is then lifted on a wide pronged fork, called a faucet, and put into the arch to be tempered, where it is ranged with many others set up edgewise, and supported by iron frames to prevent their bending. From four to six hundred tables are placed in one kiln.

A sketch of the interior of a crown-glass house, during the progress of these operations, has been given in Plate CCLXVIII. fig. 1.

The kiln having been clayed up, the fire is permitted to die out, and the heat diminished as gradually as possible. When the glass is properly annealed, and sufficiently cold to admit of its being handled, it is withdrawn from the oven, after the removal of the wall built into the front of the arch, and is then quite ready for the glazier's use. It is first, however, removed to the manufacturer's warehouse, where the circular sheets are cut into halves, and assorted into the different qualities, known to the tradesmen by the names of seconds, thirds, and fourths.

We conclude our remarks on the manufacture by observing, that the quality of glass does not depend upon the mixtures alone, but also upon the treatment it receives after it has been made, the quality of the coals, and management of the furnaces. Cleanliness in every department of the manufacture, a general knowledge of chemistry, and of the art in all its details, with the most unremitting industry, and skill in the direction and government of the operatives, are all essentially necessary for the production of good glass.

MANUFACTURE OF BRITISH SHEET-GLASS.

This article is only manufactured by Messrs Chances and Hartleys, of West Bromwich, near Birmingham, who, after having visited the glass manufactories of France, Belgium, and Germany, commenced, in 1832, the making of British sheet. The principle upon which it is manufactured is the same as that acted upon in the making of common or green glass. The metal is formed into cylinders, and then flattened into sheets. The French, Belgians, and Germans, having pursued this system for the last fifty years in making their window-glass, have much improved the old mode of making it; and as the parties who are now manufacturing this article in England are crown-glass makers, and have imported all the improvements adopted in the making of sheet-glass in France, Belgium, and Germany, and combined with these the improvements which their experience as crown-glass makers had taught them during the same period, they have surpassed the French, Belgians, and Germans in sheet-glass, and can now compete with them in all parts of the world.

There is no crown-glass made in France; and their window-glass, though superior to our broad or common glass, is not equal to the British sheet. In Germany there is little crown-glass made, and that of a very inferior quality. The greater part of the glass made in that country is sheet, and it is of much better quality than the French or Belgian. In Germany a common sort of glass is made, in the following manner: Three or four workmen form a partnership, and, having fixed upon a place in the woods where clay and sand are easily met with, they proceed to build a glass-house with wood and clay. They then make the pots, and, from the ashes of the wood which they burn, obtain potash, which, after it has been mixed with sand, they melt into glass. They blow the metal into cylinders, flatten it into sheets, cut, pack, in short, perform the whole operations from first to last, themselves. A good deal of the best of the glass made in this manner is sent to Nuremberg, where it is polished and sent into Holland. Some of it is sometimes smuggled into this country, and is known by the designation of Dutch glass. The expense of making British sheet is about the same as making crown-glass, excepting in the case of large squares, when it is much less; in crown-glass it is very difficult to get a square $34 \times 22$, but in sheet-glass the common size is $40 \times 30$; nay, sheets are sometimes made as large as $50 \times 36$. Its other advantage over crown is, that it has none of that wavy or curved appearance, by which the vision is so much distorted in crown-glass; but, at the same time, sheet-glass has rather an unpleasant appearance when viewed from the outside of a building, in consequence of an unevenness of surface, technically termed 'cockled'; when viewed, however, from the inside, it is difficult to distinguish it from plate-glass.

The materials employed in the making of sheet-glass are the same as those used in the making of crown-glass. The large melting furnace is also very similar; in France and Belgium they usually contain six or eight pots, but at the manufactory at West Bromwich the furnace contains ten pots, each containing seven cwt. of metal, which requires fourteen hours to melt.

In a line with each pot, and four feet from the ground, are erected ten stages, with an open space between each, of about two feet, through which the workman swings his glass when making cylinders. When the metal is ready for working, the ten workmen take their stations, each having his own pot and stage, and also an assistant, and commence making the cylinders, as follows: After gathering the quantity of metal required (which varies from three to twenty pounds), the workman places it in a horizontal position upon a wooden block, which has been hollowed, so that, when the workman turns the metal, it shall form it into a solid cylindrical mass. In the mean time, the assistant, with a sponge in his hand, and a bucket of water by his side, lets a fine stream of water run into the block, which keeps the wood from burning, and also gives a brilliancy to the surface of the glass. The water, the moment it comes in contact with the glass, is raised to the boiling point, and, in that state, does no injury to the metal; but it is only when the metal is at a high temperature that such is the case; for, whenever the glass is cooled to a certain degree, it immediately cracks upon coming in contact with water. When the workman perceives that the mass of metal is sufficiently formed and cooled, he raises the pipe to his mouth at an angle of about seventy-five degrees, and commences blowing it, at the same time continuing to turn it in the wood block, till he perceives the diameter to be of the requisite dimensions, which are usually about ten inches. He then reheats this cylindrical mass, and, when it is sufficiently softened, commences swinging it over his head, continuing to reheat and swing till he has made it the desired length, which is commonly about forty inches. It is now in a cylindrical form, forty inches long and ten inches in diameter, one end being closed, and the other having the pipe attached to it. The workman now begins to open the end which is closed, for which purpose he encloses the air in the cylinder, by stopping the aperture of the pipe with his finger; and then placing the closed end of the cylinder towards the fire, it becomes softened, while at the same time the air within is expanding, and, in about thirty seconds, the glass becomes too soft to retain it, and bursts, a small aperture being formed at the point of the cylinder. The workman then turns the cylinder round very quickly, and, by keeping it warm at the same time, flashes it out perfectly straight; the other end, which is attached to the pipe, has now to be cut off. This is done in the following manner: The workman having gathered a small quantity of metal on the pontil, draws it out into a thread of about one eighth of an inch in diameter, laps it round the pipe end of the cylinder, and, after letting it remain there for about five seconds, withdraws it suddenly, and immediately applies a cold iron to the heated part, which occasions such a sudden contraction, that it cracks off where the hot string of glass has been placed round it. The workman having now formed a perfect cylinder of forty inches in length and ten in diameter, has before it can be flattened, to split it on one side, so that it can be opened out; but before doing this, he is obliged to let it cool, and then, laying the cylinder horizontally upon a bench, draws a red hot iron two or three times along the inner surface. The cylinder, thus heated, immediately splits along the heated part, owing to the expansion of the glass when heated, its cylindrical form preventing its breaking at the point of expansion.

The blower having now completed his cylinder, hands it over to the flattener to make it into a flat sheet; to accomplish which, two furnaces are built together, the one for flattening the cylinders, the other for annealing the sheets, the former being kept at a much higher temperature than the latter. The cylinder, after being gradually reheated, is placed in the centre of the flattening furnace, upon a smooth stone, with the cracked side upwards. In a short time it becomes softened with the heat, and by its own weight falls out into a flat square sheet of forty inches by thirty. The flattener, with a piece of charred wood, rubs it quite smooth, and then places it in the annealing arch, where it remains about three days to be annealed. A workman will make sixty cylinders $40 \times 50$ in one day; and a flattener can flatten the same number in the same time. This glass can be made of any thickness from one twentieth to half an inch; but, in consequence of the heavy duty in this country, it is seldom made more than one twelfth of an inch in thickness, crown-glass being about one sixteenth.

The same enterprising company also manufacture large oval and square British shades, used for covering French clocks and other ornaments, and commonly called French shades. We believe they are the only persons in this country who do so, as, till within the last two years, we have been supplied entirely from France. From their being made in England, and greatly decreased in price (being fifty per cent. cheaper than when imported from France), this beautiful ornament is now becoming very generally used.

There is another species of glass called broad or common window-glass, which is formed of the coarsest materials. The ingredients usually employed are, six measures of soap-boilers' waste, three of kelp, and three or four of sand. After these have been fitted for from twenty to thirty hours, they are removed while red hot to the pots in the working furnace, where, in the space of from twelve to fifteen hours, they are reduced to a fluid state. The metal is taken out in the manner already described, and blown into globes about a foot in diameter. A piece of iron dipped in cold water is run along them, and produces a crack nearly rectilinear; and, while yet warm and ductile, these spheres are opened out and flattened on a smooth iron plate at the mouth of the furnace.

**MANUFACTURE OF PLATE-GLASS.**

This description of glass may be manufactured in the same manner as broad window-glass, or by casting the materials in a state of fusion upon a flat surface. Little correct information has been published relative to the manufacture of plate-glass, from the reluctance of proprietors to permit their works to be examined by individuals capable of giving an intelligible account of them. If such are permitted to scan the mysteries, they are generally restricted to keep secret the information which they have acquired. The late Mr Parks the chemist, however, seems to have been exempted from this condition, and having visited the premises of the British Plate-Glass Company, at Ravenhead, in Lancashire, he has published a short account of the process as there carried on. Besides the above manufactory, there are other two in Great Britain; Messrs Cookson and Co.'s, South Shields, and W. A. A. West's, Eccleston, near St Helen's; and plate-glass is also made at the celebrated works at St Gobain in France, besides other places upon the Continent.

The following is Loyset's account of the relative proportions of the materials used at St Gobain, in the manufacture of plate-glass. White sand, 100 parts; carbonate of lime, 1 ditto; soda, 45 to 48 ditto; fragments of glass of like quality, 100 ditto; oxide of manganese, ½. The following proportions of ingredients are said to produce the best description of this article. Lynn sand which has been well washed and dried, 720 parts; alkaline salt containing 40 per cent. of soda, 450 ditto; lime slaked and sifted, 80 ditto; ore, 25 ditto; broken plate-glass, 425 ditto. These quantities produce one pot of metal which yields 1200 pounds of glass.

Great nicety must be observed in conducting the processes of this manufacture. The materials must be selected with the utmost care. The sand should be of the whitest and finest description, and well washed and passed through a sieve, previously to being mixed with the other ingredients. Soda is always preferred to potash, because it imparts a higher degree of fluidity to the glass, and also because the impurities which it contains are more easily dissipated by the heat. Lime acts as a flux, and manganese has the effect of giving a slightly reddish hue to the mixture by which the colours of the other materials are neutralized, so that scarcely any appreciable tint remains. Cobalt is likewise used in some manufactories, much for the same purpose as manganese. The broken glass, or cullet as it is technically called, is those fragmentary portions which are cut from the plates when they are squared, that which may flow over in the process of casting. The red, lime, soda, and manganese, being properly mingled in the proportions above given, are fitted in small furnaces, where the temperature is gradually raised to a red or white heat, and there maintained until no more vapour is evolved, nor change undergone by the mixture. This process occupies six hours, and after its completion the other ingredients are added, consisting of cullet and cobalt. At St Gobain there are two kinds of crucibles employed; the one in which the glass is melted is called a pot, and has the shape of an inverted truncated cone; the other is entitled a cuvette; it is kept empty in the furnace, and exposed to the full degree of heat. Forty hours are requisite to vitrify the materials properly, and bring the glass to a fit state for casting.

The pots are skimmed in the manner already described. When the liquid mass has been properly refined, the cuvette is filled by a copper ladle, and after sufficient time allowed for the bubbles created by this disturbance to escape, it is removed to the table where the plates are cast. Copper was the metal of which tables were formerly constructed; but cast iron has now been found to answer the purpose completely, and it is greatly superior to copper in this respect, that it remains uninjured during all the sudden transitions of temperature to which it must be subjected.

The British Plate-Glass Company were the first to produce this improvement. They procured a plate fifteen feet long, nine feet wide, and six inches thick. The sides provided with metallic ribs, the depth being exactly the measure of thickness which it is desired the glass should have. During the casting there is a similar rib temporarily attached to the lower end of the table. The cuvette being filled with melted glass, it is withdrawn from the furnace by means of a crane, taken to the upper end of the casting table, and after being properly scummed, and elevated to a sufficient height by means of a crane, it is emptied of its contents. The surface of the melted matter is then smoothed by means of a large hollow copper cylinder, which extends across the table, resting upon the side ribs. This is set in motion, and rolled over the glass, by which process it is spread out into a sheet of uniform breadth and thickness. When the plate has become completely hardened, it is carefully inspected, to see that no flaws or bubbles appear on the surface. Should any be found, the sheet is immediately divided by cutting through them. It is afterwards removed to the annealing oven, where it is placed in a horizontal position, and remains for about fifteen days. When glass is in a high state of fluidity it is liable to be injured even by a draught of air, so that the apartment must be kept as free as possible from disturbance. The opening or shutting of a door, by setting the air in motion, might impair the value of the plate. After having been withdrawn from the annealing oven, they have to undergo the operations of squaring, grinding, polishing, and silvering, before they are fit for the market. These processes have thus been described by a late writer upon the subject.

"The first process—that of squaring and smoothing the edges—is performed by passing a rough diamond along the surface of the glass, guided by a square rule; the diamond cuts to a certain depth into the substance, when, by gently striking the glass with a small hammer underneath the part which is cut, the piece comes away; and the roughnesses of the edge then left are removed by pincers. The plate is then taken to the grinding apartment.

"The next step is to place each of the plates upon a table or frame adjusted horizontally, and made of either freestone or wood, cementing the glass securely thereto by plaster of Paris. One plate being then reversed and suspended over another, the material employed in grinding their surfaces is introduced between the two, and they are made to rub steadily and evenly upon each other by means of machinery set in motion by a steam-engine." River sand and water were formerly used for the purpose of abrading the surface, but ground flint is now substituted, as answering the purpose better. When one side of each plate has been sufficiently ground, it is loosened from the frame, and turned over, so as to present the other surface to be ground in the same manner. Some degree of pressure is employed, by loading the upper plate with weights, as the grinding of each side approaches to completion. The process thus described used formerly to last during three entire days, but this time is now much abridged. The greatest attention is required in order to finish with the surfaces perfectly level and parallel, for which end a rule and plumb-line are employed.

By means of this grinding, the plates will have been made level; but they are too rough to receive a polish. To fit them for this, they must again be ground with emery powder of increasing degrees of fineness. The preparation and sorting of this powder are effected in the following simple and ingenious manner:—"A considerable quantity of emery is put into a vessel containing water, and is stirred about violently until the whole is mechanically mixed with the water. Emery is absolutely insoluble by such means; and if the mixture were left at rest during a sufficient time, the whole would subside in layers; the coarsest and heaviest particles sinking first, and so on successively, until the very finest particles would range themselves as the upper stratum. Previously to this, however, and while these finest grains are still suspended in the water, it is poured off into a separate vessel, and the emery is there allowed to settle. A fresh supply of water is poured into the first vessel, the contents of which are again violently agitated, and allowed partially to subside as before. A shorter interval is allowed for this than in the first case; and then the liquor is poured off into a third vessel, by which means emery of the second degree of fineness is separated. This operation is repeated in order to obtain powders having four different degrees of fineness. The deposits are then separately dried upon a stove to a consistence proper..." for making them up into small balls, in which form they are delivered to the workmen.

"In this further rubbing together, or, as it is called, smoothing of the glass plates, it must be understood that the coarsest emery is first used, and so on, substituting powders having increasing degrees of fineness as the work proceeds."

These processes finished, the glass, although perfectly even, appears opaque or deadened on the surface, and requires polishing. This is effected in the following manner. A piece of wood is covered with numerous folds of woollen cloth, the layers being divided by some carded wool interposed between each, the whole forming a tolerably hard but elastic cushion, which is furnished with a handle. The plate is laid upon a bed of plaster, as already described, and the cushion being wetted, is covered with the red oxide of iron (the coelothar of commerce), and moved backwards and forwards upon the surface of the plate. Lastly, if the glass be intended for mirrors, it is silvered, that is, covered on one side with a thin coating of mercury.

The process of blowing plate-glass differs so slightly from the methods used in producing broad glass that they need not be here repeated. Any difference that does exist, arises from the great bulk and weight of the mass of glass operated upon.

STAINED AND PAINTED GLASS.

The invention of the art of colouring glass, that is, imbuing it throughout with any particular tint, seems, as we have already had occasion to remark, to be nearly coeval with the discovery of the art of making the substance itself; Egyptian ornaments, and druidical beads, of the highest antiquity, as already mentioned in our historical notices, having been found of numerous and surprisingly beautiful colours. The art of staining and painting glass so as to form pictorial representations of objects, is, however, of comparatively recent date. The precise period of its introduction is unknown, but it is at least certain that it has existed for many centuries in different degrees of excellence, and that it has moreover been gradually advancing in improvement. The earliest record which we possess concerning the existence of this beautiful art is of the age of Pope Leo III., that is, about the year 800, a period which witnessed the erection of many of the most magnificent ecclesiastical edifices upon the Continent. Several centuries, however, elapsed before stained glass came into general use. The earliest specimens with which we are acquainted differ from those of more recent date, inasmuch as they are composed of small pieces of glass imbued throughout with colour during the process of manufacture, and to which artists give the name of pot metal.

These were united by joinings of lead after having been cut to the required shapes, and are thus made to form a species of Mosaic work; but, as might be expected, they do not possess that breadth of colour, or truth and delicacy of effect, which the improvements of more modern artists have enabled them to communicate to their works. The manufacture of stained glass was for many centuries confined to the Continent, and was nowhere prosecuted with so much success as at Venice. At the same period that the pointed style of architecture reached the meridian of its splendour in England, we find native artists who were fully qualified to do justice to the grandeur of the buildings they were called on to adorn, and not unworthy of being put in competition with their most successful foreign rivals. In proof of this we need only refer to the windows of York Minster, of the collegiate chapels and halls of Oxford, and those of the chapel of King's College, Cambridge. A pretty general, but very erroneous, idea exists with regard to the superiority of the colours employed in ancient glass painting over those in use at the present day. It is believed by many, and taken for granted by others, that not only is the same brilliancy unattainable by modern skill, but that the art of producing the colours themselves is itself entirely lost. This is a very mistaken notion; for not only are those now employed as brilliant and durable as the colours of the ancients, but others have been added, which they most probably did not know how to produce, or at least did not use. Amongst these are pink, straw colour, and other compound tints. That indiscriminating veneration for the antique, which has so often and so seriously interfered with the claims of modern art to the encouragement to which it is entitled, has operated against glass painting and staining with perhaps fully more force than against any other art. It has induced a belief that excellence in the art is confined to the ancients; and that all the productions of the modern glass stainer and painter are mere flimsy imitations of those of the artists of the fourteenth and fifteenth centuries. Nothing farther is necessary to convince any one of the injustice and absurdity of this notion, than a visit to the warehouse or workshop of any respectable glass painter and stainer of the present day.

The following observations are deserving of the attention both of artists and others less immediately interested in the subject. "Captivated with the vivid hues of the antique, persons have remarked, with more frequency than judgment, 'such colours certainly cannot be equalled in the present day.' With the exception, perhaps, of its reference to the ancient ruby, which appears to have been lost for the past two centuries, this assertion may be altogether denied; and more than this, besides commanding all the resources of the old artists, ours of the present day are in possession of many practical advantages which the former had not, among which is that of their being able to lay every variety of colour on one and the same piece of glass, and thus often to execute with nicety in ten pieces a subject on which a hundred formerly would not have been so well bestowed. With these opportunities, and with greatly improved ideas upon the science of painting in general, our artists should be qualified for productions of a higher order than those of their ancient predecessors; and it remains, then, to be asked, on what account they fail to imitate their works with success. The chief occasion of this may be found in the imperfect acquaintance which the modern artists have with the principles of old English design, both pictorial and architectural. They seem to forget that these principles are totally distinct from those observed in the paintings of the later Italian masters, whose figures and groups are not unfrequently copied for the embellishment of our windows in the pointed style, but always without success. Strict simplicity, solemn dignity, and appropriate costume, are primary points for consideration in imitating the figures of our old windows. In the imitation also of those architectural decorations with which such figures were anciently surrounded, it is worse than puerile to suppose that mouldings and foliage borrowed from the Greek and Italian systems can by any possibility be so arranged as to bear a resemblance to the characteristic features of the old English style, a style as isolated as it is magnificent. Errors such as these can only be avoided by means of patient and attentive study, both of actual remains and of the numerous explanatory works now rendered generally accessible by the invaluable labour of able antiquaries and

1 Glass Manufacture, Lardner's Cabinet Cyclopædia, No. 26. But after an adequate acquaintance with principles of design is attained, those of execution are less to be observed; all the subjects of the painting, especially those of an architectural character, being revered more by strong black outline and variety of color than by the use of decided shadows. Modern imitations are frequently injured by displaying too much of modern art; the work, by being too highly finished, and set in few pieces, often loses the glittering effect that attends its more simple prototype. An additional precaution to be observed consists in the avoidance of excessive depth of colour; a consideration, the neglect of which has given some modern imitations a vulgar, gaudy appearance, totally dissimilar to the equalised and subdued, yet lively colouring, observed in the best specimens of the middle ages.

The want of harmony here complained of is too often offensively manifest in modern public buildings, which have been fitted up with stained-glass windows, and where the absurd incongruities of style have marred rather than increased the elegance of the structure. Florentine meaningless mouldings, scrolls and foliage, are seen disturbing the simple beauty of Grecian architecture, or the austere and majestic grandeur of a Gothic pile; so that people seem to have been careless as to the character or propriety of the ornament, provided they did but procure something in the shape of stained glass. No doubt much of this evil is to be attributed to the unskillfulness of the artists employed, few of whom are possessed of a sufficient knowledge of design, or the more intricate principles of the pictorial art, to enable them to suit their embellishments to edifices of a noble or commanding character.

The disadvantages inherent in the art itself tend to debar from engaging in it men whose talents as painters ensure them patronage and success by adhering to the palette and the canvass. The expense of materials; the tedious and precarious nature of the process, where the artist cannot watch with satisfaction the effect which each additional stroke of his brush gives to the work as it grows beneath his hand; but must await in suspense the result of its exposure in the kiln; the difficulty of introducing such works into general notice; and the uncertainty of ultimate remuneration for his labours; prevent the man of genius from prosecuting an art, which nevertheless presents the most favourable opportunities for the expression of his ideas. There are not wanting, however, specimens of distinguished excellence produced by modern skill in higher branches of this art, especially in the historical department. They certainly do not possess that melodic richness of colour, that calm and imposing grandeur of character, which distinguishes many of the older productions, but they excel them in accuracy of drawing, in details; and while we know that it is perfectly possible to combine the various excellencies of former artists with those of a more recent date, we do not despair of seeing greater triumphs achieved in the art of staining than have yet been effected. Every variety of subject may be executed in this style. To the landscape painter it offers peculiar advantages, from the powerful contrasts in light and shade which it enables him to produce; while to the painter of flowers it affords means wholly unequalled for displaying the delicacy and the same time splendour of colour, which his prototypes in nature place before his eyes.

It is somewhat strange, that while almost every other art has been called on to contribute in some way or other our domestic comforts, or to the adornment of our dwellings, that of glass painting and staining, though its productions are not more expensive than many of these, and are certainly not inferior in elegance, should yet be rarely applied to domestic purposes, where it could be employed with admirable effect. When stained glass has been used in the embellishment of the mansions of the middling, or even of the upper classes, it has been hitherto in a great measure confined to hall and staircase windows, and to windows placed in similar situations; but its use might be much extended, with great advantage in point of ornamental beauty.

If, for instance, the windows of a room were filled with stained glass, whose prevailing tints should harmonize with the predominating colour in the apartment, a striking and singularly pleasing effect would be produced. Where the expense, or any other objection, might be urged against figured glass, in which masses of brilliant colour are employed, that description which is plain and of one tint, such as brown, ruby, pale yellow, or similar hues, might be substituted; and if selected with reference to the prevailing colour of the interior with the view of either heightening or deepening its complexion, a warmth and richness of tint would be thrown around the apartment, such as no other contrivance of art can communicate. And where both of these descriptions of coloured glass might be found unsuitable, either from the expense or the too great exclusion of light, there is a third description of ornamental glass which might be employed, and which is not subject to these objections. This is a pale tracery, resembling lacework, which, when properly executed, is exceedingly beautiful, and is marked by an appearance of singular lightness and elegance. The introduction of such windows as might thus be produced would greatly enhance the beauty of our domestic architecture.

Except in the name, painting on glass has no resemblance to any other department of the pictorial art but that of porcelain. Both the colours, and the process of their application throughout, are entirely different. While animal and vegetable substances are freely used as colouring matter in every other department of the pictorial art, they are wholly excluded in that of glass painting, where all the pigments used are subjected, after being laid on, to the operation of fire, to make them penetrate the body of the glass, or become fused on its surface—a process which would wholly destroy the colouring properties of such substances. All the colours employed in glass painting and staining are oxides of metals or minerals, as gold, silver, cobalt, which not only stand the fire, but require the powerful interference of that agent to bring out their brilliancy and transparency. Some colours, on the application of heat, penetrate the body of the glass, and, from this circumstance, are called stains; while others, being mixed with a vitreous substance called flux, become fused or vitrified on the surface. The former produces a variety of colours, and all of them are perfectly transparent. The produce of the latter are only semitransparent, but they may be made to yield any colour or tint required.

In preparing these colours, the most important point to be attended to is, to have all those that are to be used at the same time of an equal degree of softness. To attain this, those that are hard, and require a great degree of heat to make them effective, must be fixed first; leaving the soft colours, for which a slight heat only is necessary, to the last. If used promiscuously, and without regard to this precaution, some of the colours would be rendered too fluid, while others would be insufficiently fused, and the work in consequence spoiled. It is likewise of great importance to make a proper selection of glass for the purposes of staining and painting, as one kind will assimilate more freely with one colour than with another. The description of glass generally chosen for painting or staining is the best crown-glass.

It does not seem necessary to enter at length here into the details of the process of glass painting and staining, as our account of the processes and mixtures must of ne- cessity be almost entirely a recapitulation of what has been more fully and satisfactorily stated in other works, than the space allotted to this part of the subject would permit us to do; while all such details would be nearly useless for any practical purpose, there being scarcely a possibility of either communicating or acquiring such a knowledge of the art of glass painting or staining as would enable any person to understand or practise it successfully, unaided by personal observation and extensive experience.

CROWN-GLASS CUTTING.

This is a subject of very great importance to the glazier. Since the sheets of glass are circular, and the panes of glass most commonly used of a square or oblong shape, it is evident that there must some waste result from cutting up a sheet. The grand object of the glass-cutter, therefore, in the first place, is not only to cut up the sheet into panes which shall produce the least waste, but also, since the sheets of glass vary in size, to know what panes can be obtained from a sheet of a given diameter. To the glass-cutter this is well known, and to the general reader it can scarcely be explained so as to be completely understood. The utensils necessary for this purpose are a cross cutting board and a breaking out board, both of which are graduated or indented with brass lines in such a manner as to show through the sheet of glass, when laid on the cutting table, how many panes of one size, and how many of another, may be obtained from a sheet of given dimensions: squares and laths, on which feet, inches, and fractional parts are marked, are also necessary.

Crown-glass always cuts best in a warm temperature. When it happens to be hard, which is seldom the case (a bad diamond, or not knowing how to use a good one, being the usual cause of breakage), it has been found to cut better after warming the glass before the fire, which has the effect of diminishing the tension of the ill-annealed glass.

GLAZING OF WINDOWS.

Before proceeding to speak of glazing, the order in which its various processes present themselves naturally demands that we should say something of putty.

This important and indispensable article in the glazier's trade is composed of whiting and linseed oil. Chalk is sometimes used instead of the former, but the expense and labour incurred in preparing it is much greater, and besides it is generally mixed with sand, so that it is no object to the glazier to employ it. Whiting is in every way to be preferred; it must be thoroughly dried before the oil is added to it; otherwise the union will not be effected, or at least it will be very imperfect.

After the whiting has been thoroughly dried and prepared, it ought to be passed through a very fine sieve, and all the lumps and knots that remain pulverised, and then also passed through the sieve. Great care must be taken to keep the whiting free of sand and other extraneous substances.

When putty is to be made, put the proper quantity of oil into a tub or other open vessel, and gradually add the whiting whilst yet in a hot state, at the same time keeping the whole in motion with a stick, until it becomes of a sufficient consistency to admit of being wrought by the hand on a board or table. Having been removed thither from the tub, it must be wrought up with dry whiting, until it is converted into a solid compact mass. When brought to this state, it ought to be put into a hollowed stone or mortar, and beat with a wooden mallet till it becomes soft and tenacious, when more whiting must be added, until it has attained a proper consistency.

It is considered that the putty is improved if the whiting and oil, after being mixed, are allowed to remain for about twenty hours before being wrought up. After putty has been made, it should be firmly packed in a cask, from which it may be taken from time to time, as it is required. It ought not to be used for ten or twelve days after it is made, when its colour, from having at first been a dull yellow, will have changed to a whitish free-stone, which renders it more suitable for most purposes. After a lapse of six or eight weeks, the putty in the cask will become hard; but it is easily restored to its original softness, by being beat as before, and it is much improved by this second operation.

Putty is made in England in large quantities, and is ground in a mill in the same way as white lead; but this is no improvement, as it is generally overworked in this method of preparation, and rendered so tough and tenacious that it does not work well, and is entirely without that degree of pliability which putty ought to possess.

When putty is required of a superior degree of fineness, and which will also dry quickly, add a little sugar of lead, or litharge; and if an increase of strength be wanted, a little white lead.

We now proceed to glazing.

To glaze well, neatly, and expeditiously, simple as the operation may appear, is an art for the thorough acquirement of which many years of practice are necessary.

When a glazier receives an order to glaze a house, he must first, of course, proceed to measure the work to be done. In doing this, he must take the full size of the panes, that enough may be left for stripping, so as to produce an accurate fit into the sashes. This fitting must be performed with great care and nicety, leaving about one thirty-second part of an inch of space on each side and end of the pane, between it and the check. In other words, the pane must fill the space appropriated for it, to within the thirty-second part of an inch, or thereabouts.

This space is left to provide for such occurrences as the wood swelling with moisture, or the building settling, in which cases the panes would be apt to crack.

When the panes have been fitted into the checks of the sashes in the manner spoken of, they must be removed, and the checks well bedded with heat putty. This done, the panes are again returned to their places, and gently pressed or lodged into the bedding, the workman, as it were, humouring the glass should it be bent or twisted, and taking care that there is no hard extraneous substance mingled with the putty, which might endanger, if not actually break, the glass. When a pane is perfectly bedded it lies quite firm, and does not spring from the putty; but when, either from a perverse bend or twist in the glass, or any other accidental cause, it happens that it cannot be made to go quite close to the check, the vacant space must be carefully and neatly filled upon the back puttying, otherwise the window will not be impervious to the weather, and will be very apt to fall into decay by the admission of moisture.

It may not be superfluous to observe here, that the convex or round side of the pane, where such a shape occurs, should be presented to the outside, and the concave or hollow to the inside. The reasons for recommending this disposition of such panes are so obvious that they need hardly be enumerated. It may, however, be stated generally, that when thus placed, they resist the weather better than if the hollow sides were exposed to it.

After the pane has been bedded, the next process is the This putty should be kept in the fore- cask, about the thirty-second part of an inch below the feel of the inside cheek, so as to allow the thin layer of put which binds these two substances together to join the putty and glass; and that it may not offend the eye by being seen from the inside; and that, when it is applied, the brush may not encroach on any visible part of the pane, leaving those ragged lines or marks which are often seen from the inside on ill-finished windows, which are so displeasing to the eye. This operation, as finishing the corners, are two nice points in the art, therefore, when properly done, discover the neat- handed and skilful tradesman.

It is the opinion of some experienced glaziers, that the inside puttying, which is the next process, ought to be al- lowed to remain eight days before being finished off, while others, again, say that this should be immediately done. The experience of the writer inclines him to the former opinion. By standing over for some little time, the putty acquires a hardness which admits of a better and neater finish than when it is in the soft working state, and in this way it is not liable to shrink. Of course this is only recommended in cases of extensive jobs. When only a few panes are done, it is better to finish them off at once, in order to subject the employers to the inconvenience of a second visit from the glazier for trifling purposes.

When the finishing does take place, however, the putty must be cut clean off with the putty knife, and on a level with the style of the astragals. Complete the work by cleaning the glass and putty with a 000 duster brush, which removes all dust and loose putty from the pane, thoroughly and effectually.

**Hot-House Glazing.**—The frames or sashes of a hot- house ought, before being glazed, to receive two coats of white paint, to which a small portion of red lead has been added to facilitate its drying, and to give increased strength and durability to the paint.

The panes in the roofs of hot-houses are generally of one of three forms; the first is the square pattern; the second is the tapered, that is, terminating in an obtuse angle; and the third the semicircular. The first is most generally used; the second is considered an improvement on the first, in so far as the tapered point carries off the rain down the centre of the pane, and thereby preserves the astragals; but there is a loss in shaping the glass to the tapered point. The third or semicircular is decidedly the best pattern of the three; the water is not only carried down to the centre of the pane, and the astragals protected from the rain, but this pattern has a more elegant appearance, when uniformly glazed, than either of the two other shapes. There is no loss in cutting the glass to the curve, and it is therefore not more expensive.

The dimensions of hot-house panes are generally about 12 inches, and are made to overlay each other, to an ex- tent regulated by the circumstance of their being putted or not.

If it is intended to fill in the overlays with putty, they should not be more than a quarter of an inch in depth; but if it is not intended to putty them, they must then be at least five eighths of an inch.

The overlays, however, ought always to be putted, and not for two reasons. First, because it will more certainly secure their being water-tight; and because, in the next place, it will prevent the breakage to which the panes are liable from the freezing of the water, or moisture, which lodges in the overlay, and, expanding, shivers the glass in all directions; when they are filled with putty, such an accident cannot happen.

In glazing hot-house roofs, it must be observed, that the courses ought to run from end to end, and that the smaller panes, when such are used, should be reserved for the top.

When sashes are glazed, they ought to stand for eight or ten days before taking off the back putty, and they ought not to be painted for about three weeks afterwards, that the putty may consolidate. Great care, too, should be taken, when the sashes are newly glazed, that they be not in any way twisted or bent, as such an accident would almost inevitably start the panes from their beds, and thus render them pervious to water.

When sashes are of considerable dimensions, say about six feet by three, they should be strengthened by having two iron rods placed across them at equal distances, and screwed to the astragals. This will serve to prevent the accident of twisting, to which such frames are extremely liable, and which is very injurious to them after they have been filled with glass.

The putty used for glazing hot-houses ought to be of the very best description, as, from the circumstance of its position, it is necessarily more exposed to the action of the weather than in the perpendicular windows. The putty used for filling in the overlays ought to be of black or lead colour, which, as every glazier knows, is imparted to it by working it up with lamp-black; but as this sub- stance has the effect of weakening the putty, the defect may be remedied by adding two pounds of white lead, ground in oil, to each stone of putty, and in a similar pro- portion to smaller or greater quantities. Indeed all putty used in glazing hot-houses ought to have a portion of white lead mixed with it, as it adds greatly to its strength.

**Lattice or Lead Windows.**—This antique and singularly beautiful style of glazing has unaccountably fallen much into disuse, although of late years it has certainly under- gone something like a resuscitation, in consequence of a revival of the public taste for stained glass, and a growing preference for Gothic architecture in churches, cottages, and the like. For these, and for staircase windows, and indeed all windows similarly situated, as in halls, lobbies, or the like, it is peculiarly adapted.

It may be proper to premise, that lead windows require stained or coloured glass for producing their fullest and best effects, and it was with stained glass only that they were originally constructed; but very neat and elegant windows are executed in this style with plain glass, where variety and beauty of figure are made to compensate for the absence of colour.

Lead windows may be made to any pattern, and in this there is great scope for the display of a correct taste. In the time of Elizabeth, this branch of the glazier's art was carried to great excellence, especially by one Walter Geddes, who was employed in glazing most of the royal and public buildings of that period. This person execut- ed in this style some windows of transcendent beauty, displaying an endless variety of the most elegant and elab- orate figures. The most useful and most common de- scription of plain glass lead windows, however, are those of the diamond or lozenge shape; but, as already said, they may be made to any pattern desired. The follow- ing are a few specimens of lattice windows. (See Plate

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In taking out old glass from windows, the cold putty knife is used; but when the putty has been in the windows for ten or twelve years, it becomes nearly as hard as stone, and impenetrable to the knife. In this case there are various means used to extract the glass from the frames. The application of hot iron to the putty is sometimes adopted; but this cannot with safety be applied to the bedding, to which the glass obstinately adheres. Muriatic acid diluted with water is an excellent means of removing putty from glass, its action being assisted by rubbing the putty occasionally with a bit of stick. The most effectual way to remove the glass, when the frames are worthless and the glass valuable, is to put the frames into a horse dunghill, keeping the whole damp (if the wea- ther is not so) for several weeks, which completely loosens the glass, and rots or destroys the frames. Fig. 1 is the east window of St Giles' Church, Edinburgh. Fig. 2 is a less imposing, but still a very chaste and beautiful, specimen of a lattice window. This has a beautiful effect by introducing stained glass into the long skittle-shaped pieces, and in the rosette in the centre. Fig. 3 represents the architecture of a window in Oxford Cathedral, filled with stained glass in the Gothic style.

The lead work can be adapted with ease to any pattern that may be chosen for the glass; and it can likewise be made to any breadth, from one eighth to five eighths of an inch. The one eighth, however, is only used for fancy work, and is not as yet much in demand; that which is most generally used is three-eighth lead. This width makes neater and better work than that of any other dimensions.

The glazier may purchase prepared leading for windows in any quantity; but he will produce it himself at half the cost, and probably more to his own satisfaction. The apparatus and tools necessary for doing this are, a glazier's vice, or lead mill, moulds for casting the lead into slender bars or rods of about eighteen inches in length, which is the first process; a three-fourth inch chisel; a hard-wood fillet for forcing the glass into the grooves in the lead frame-work; and an opener or wedge tool, made also of hard wood, or ebony, for laying open the grooves for the reception of the glass; two copper bolts for soldering, the end formed like an egg. A correct delineation of the vice or mill alluded to is given in Plate CCLXX., in describing which, in its various connected parts, the same letters of reference are adapted to the different figures, so far as necessary, which, with the isometrical views, will facilitate the comprehension of their parts and properties.

Fig. 1, an end view, partly open, of a mould for casting three varieties of patterns, which are thus prepared for being forced through the machine. By an ingenious construction of the handle, it is made to lock and unlock by inclined planes, acting on studs, aa. Fig. 2, a side view, also partly open; and fig. 3, an isometrical view of the mould prepared for pouring in the metal.

The metal or cast being removed from the mould, a pair of the dies (one only of each pair is represented), according to the pattern required, figs. 4, 5, 6, 7, are placed in the machine, as seen at cc, fig. 8, isometrical view. After they are put in, a thin iron cover (b, fig. 10), with an oblong hole in the middle, is put on to guide the metal into the rollers. Figs. 9, 10, and 11, represent three views of the machine as prepared for operating. In figs. 9 and 11, the metal, dd, is represented passing through the machine, which is accomplished by turning the winch handle, ee, acting on two equal sized toothed wheels, ff. On the axles of these are two rollers, gg, slightly serrated (dotted through in figs. 8 and 10); these rollers draw the metal through, while the dies give the desired form. To allow the axles and rollers to be placed in the frame or body of the machine, A, the cover, h, is removed by unscrewing the bolt, i, figs. 8, 10, 11. The toothed wheels, ff, are also taken off, by unscrewing the nuts, kk. The tempering screw bolt, l, is for adjusting the dies after they are put in their place. The screw bolts, mm, are for fixing the machine to a table or bench.

Fig. 12 is an isometrical view of the cover, h, removed to show the ports, nn, through which the axles of the rollers pass.

Fig. 13 shows the shape of the bolt used for soldering the lead windows, and fig. 14 the opener already described.

The lead intended to be employed in window making must be soft, and of the very best quality; and great care must be taken to have the moulds properly tempered, otherwise the lead will not be equally diffused in them, and the castings consequently not perfectly solid throughout, as they ought to be.

If this is not attended to, that is, if the castings are not perfectly solid, they will come out of the mill, to which they are presented after being taken from the moulds, all fretted on the edges, and thus in a state totally unfit for the purpose for which they were intended.

The castings are, as already noticed, usually about eighteen inches in length, and are afterwards extended by the mill represented by the figure above, to the length of five or six feet.

It may not be unnecessary to add, that the mill not only extends the lead, and reduces it, at the pleasure of the operator, to the dimensions required, but at the same time forms the grooves into which the edge of the glass is afterwards introduced in forming the window.

When the lead has been prepared in the manner described, the glazier ought to proceed to cut out the panes wanted. For this operation he must prepare by first outlining the full dimensions of the window, and then lining it off to the pattern required, shaping the panes accordingly. If the window is of a large size, this may be done by compartments, to be afterwards united, and thus be more conveniently wrought. Great accuracy must be observed in cutting the panes, or a very irregular panel will be produced, as those lines that ought to be parallel or otherwise will not be correctly so, which will greatly injure the appearance of the work.

When all the glass has been cut for the window, the next thing to be done is to open the grooves in the lead with the opener or wedge tool. The panes are then, in order that they may be water-tight, fastened very firmly into the grooves with the wooden fillet already spoken of (which may be fixed on the handle of the chisel or cutting tool), the parallel lines of lead being secured in their proper places on the board, when the window is of the diamond shape, by a small nail at either end, until the course is finished, when the work is permanently fastened by running a small quantity of solder gently over the connecting pieces of lead at each joint, or angular point.

When the window has been completed, it should be removed from the working board to a flat table, and there covered with a thick layer of cement, composed of white lead, lamp black, red lead, litharge, and boiled linseed oil, with a half-worn paint brush, and the composition carefully rubbed into every joint. This will render the window completely impervious to the weather, as the cement, if properly laid on, will fill every chink, where it will soon become as hard and durable as any other of the materials of which the window is composed. When this operation has been completed, clean the window with a cloth and whiting. Should the outside be wanted black, omit the blacking in the first compost; and finish by laying on the lamp black with a polishing brush.

The window, on being fitted into the frame, that is, on being set in its place in the building for which it is intended, ought to be supported with three-eighth inch iron rods, extending three eighths of an inch beyond the breadth of the frame on each side, running across it at the distance of from twelve to fourteen inches from each other, and secured to the lead frame-work at intervals, either with copper wire, or lead bands manufactured by the mill. These rods, for obvious reasons, ought to be so arranged as to intersect the window exactly at the terminating point of a row of the diamonds. For instance, if the diamonds are each six inches in length or height, the first rod ought to intersect the window at the top of the third row, or eighteen inches from the bottom of the frame, and so on, until the window be equally divided in this way throughout its whole length. If the diamond, again, be only three inches in length, then the first rod ought to pass at the top of the fourth row, or twelve inches from the bottom, this proportion of distance being, of course, maintained throughout. The usual distance is fourteen inches, but this must be regulated by the THE CUTTING DIAMOND.

Before the introduction of the diamond as an agent in cutting glass, that operation was performed by means of heavy, sharp pointed instruments of the hardest steel, and sometimes red-hot iron. These were the only contrivances known and practised by the ancient glaziers.

Considering the diamond in its relations to the purpose of the window-glass cutter, there occur some circumstances not unworthy of remark. Amongst these, it may be noticed, that the cutting point of the diamond must be a natural one; an artificial point, however perfectly formed, will only scratch the glass, not cut it. The diamond of ring, for instance, will not cut a pane, but merely mix it with rough superficial lines, which penetrate but a very little way inwards. Artificial points, corners, or lines, therefore, produced by cutting the diamond, are suited only for writing or for drawing figures on glass, such as were those used by Schwanhard, Rost, and the other old artists who were celebrated for ornamenting glass vessels. The cutting diamond does not write so on glass, from the circumstance of its being apt to engrave too deeply, and take too firm a hold of the surface, thus becoming intractable. It may further be noticed, than an accidental point produced by fracturing the diamond, is as unfit for cutting as an artificial one. Such a point will also merely scratch the glass. No point, in short, is not given by the natural formation of the mineral, will answer the purposes of the window-glass cutter.

The large sparks, as the diamonds used for cutting glass are called, are generally preferred to the small ones, from the circumstance of their being likely to possess, although this is no means invariably the case, a number of cutting points; while the very small sparks are not always found to possess more than one. Thus, if the point of the latter is worn or broken off, although the spark be turned, and reset in its socket, it will still be without the power of engraving, and consequently useless, while the former, on undergoing the same operation, will present a new and effective point.

The large sparks are called mother sparks, and are sometimes cut down into as many smaller fragments bearing the same name, as there are natural points in them. Each of these, therefore, can have only one cutting point, and are consequently only proportionately valuable to the glazier, since they cannot be restored by resetting.

The Setting of Diamonds is a process with which every glazier ought to be acquainted; nor is it an art of difficult acquirement; some practice, and a little patience, are all that is necessary.

After having selected a stone, as clear and pellucid as possible, resembling a drop of water, and of an octoedrical shape, or as near to that form as it can be procured, the workman proceeds to ascertain which is its cutting point, or, it has more than one, which is the best. This will be found to be that point which has the cutting edges of the crystal placed exactly at right angles to each other, and passing precisely through a point of intersection made by the crossing of the edges.

He then provides a piece of copper or brass wire, a quarter of an inch in diameter, having a hole drilled in one end large enough to contain three fourths of the diamond to be set. Having temporarily secured the diamond in his hole, the setter ascertains the cutting point, by trying it on a piece of glass; and when he has discovered it marks its position by making a slight notch in the wire with a file or otherwise, exactly opposite to the cutting point, as a guide to him in his operations when he comes to fix it permanently in the socket head of the handle. When doing this, care is taken to keep it exactly parallel with the inclined plane of the socket head.

The cutting point having been ascertained, and the diamond fixed into its place, the wire is then cut off about a quarter of an inch below the diamond, and filed down to fit exactly into the aperture in the socket head, into which it must be soldered. The rough or superfluous metal around the stone is removed with a file; and, lastly, the setting is polished with emery or sand paper. Such is the most approved method of setting new diamonds, and it applies equally to the resetting of old ones. But in the latter case, the first process, that of detaching the stone from its bed, is accomplished either by means of a knife, or by applying the blowpipe.

The art of managing the diamonds in glass-cutting, so as to produce effective results, can only be attained by considerable experience. The diamond must be held in a particular position, and with a particular inclination, otherwise it will not cut, and the slightest deviation from either renders an attempt to do so abortive. In the hands of an inexperienced person, it merely scratches the glass, leaving a long rough furrow, but no fissure. The glazier judges by his ear of the cut made. When the cut is a clean and effective one, the diamond produces, in the act of being drawn along, a sharp, keen, and equal sound. When the cut is not a good one, this sound is harsh, grating, and irregular. On perceiving this, the operator alters the inclination and position of his diamond, until the proper sound is emitted, when he proceeds with his cut.

Although the diamond cuts glass of an ordinary thickness with facility, it does not easily cut that which is of more than a medium thickness. In such cases, the desired division is effected by the application of a hot iron, which being brought in contact with the glass at certain points, produces a fissure in the direction required.

The diamonds employed in glass-cutting, are of the description known by the technical name of bort, a classification which includes all such pieces as are too small to be cut, or are of a bad colour, and consequently unfit for ornamental purposes. These are accordingly selected from the better sort, and sold separately, at an inferior price.

Though there are many substances that will scratch glass, the diamond was thought to be the only one that would cut it; but some experiments of Dr Wollaston have shown that this is not strictly correct. That eminent philosopher gave to pieces of sapphire, ruby, spinal ruby, rock crystal, and some other substances, that peculiar curvilinear edge which forms the cutting point in the diamond, and in which, and in its hardness, its singular property of cutting entirely lies, and with these succeeded in cutting glass with a perfectly clear fissure. They lasted, however, but for a very short time, soon losing their edge, although prepared at a great expense of labour and care; while the diamond comes ready formed from the hand of nature, and will last for many years.

MANUFACTURE OF FLINT-GLASS OR CRYSTAL.

This is the species of glass of which the finest and most beautiful articles used for domestic purposes or for ornament are made. It is also largely employed in the manufacture of optical glasses, and for other philosophical purposes. It is the heaviest, the most brilliant, and also the most costly, of all the vitrified compounds. In order to convey an idea of the manufacture of flint-glass, we propose to give an account of a work in the vicinity of Edinburgh. Our description will be best understood by fre- Fig. 1 represents a cone twenty-two feet two inches in diameter at the bottom, eight feet diameter at the top, and sixty feet in height. It contains twelve arches; \(a\) is a front view of one of them. Each of these arches contains one pot, and the whole of them are heated by means of flues which ramify round the whole cone, proceeding from one general furnace. The furnace, which is circular, is fifteen feet four inches in diameter, and six feet in height inside to the centre of the crown. Fig. 2 represents a pot which is manufactured of Stourbridge clay, of the best quality. From the bottom to the highest part the pot is thirty-eight inches in height, and the width outside thirty-four inches. The orifice of the pot measures about eight inches across. About fourteen hours are necessary before the pots can all be filled, on account of the metal sinking into less bulk as it melts. During the whole time the furnace must be kept as hot as possible. After the pots are all filled, about forty-four hours elapse before the vitrified mass is brought to a proper state for working. More or less time is necessary according to the state of the materials, and from time to time the pots must be carefully scummed in order to remove any impurities.

As in every other branch of glass making, the proportions of the ingredients used for making flint-glass vary with almost every manufactory. The following is reckoned an excellent compound. Fine white sand, six hundredweights and a half; red lead or litharge (minimum), three hundredweights and a half; calcined potash, two hundredweights; nitre, eighty-four pounds; manganese, from eight to eighteen ounces, according to circumstances; arsenic, from one to two pounds; cullet, or broken crystal, a quantity sufficient to fill up the pots. The above quantities of materials fill two pots. On the authority of the Messrs Aikin, a very excellent article may be made from 120 parts of fine white sand, forty parts well purified pearl ash, thirty-five parts litharge, thirteen parts nitre, and a small quantity of black oxide of manganese. The principal difference between flint and other kinds of glass is in there being present in its composition a considerable quantity of some metallic oxide. All metals in a state of oxidation will combine with silica and an alkali to form glass. Only lead and bismuth, however, can be employed in sufficient quantity so as to produce a bright colourless article. The other metals impart various hues to the mass. Lead being the cheapest of the two metals, is that universally employed. If it be used, however, in too great a quantity, it will not only tinge the glass of a yellow colour, but produce an inconveniently soft material.

After the metal has been brought to a state when it is fit for being wrought, the workmen commence operations. The implements which they use are few in number and simple in construction. The first tool required is a hollow iron tube between four and five feet in length, and one eighth of an inch in the bore; it is technically called the iron, and is dipped into the pot in the manner represented in Plate CCLXXI, figs. 5 and 6. After a sufficient quantity has been collected on the end of this rod, it is withdrawn from the pot and suspended for a few seconds in a perpendicular position, that the glass, which is at the under end, may be lengthened out beyond the rod. It is then rolled upon the marver. This process, by which the glass is rolled into a cylindrical form, is represented by fig. 7. The glass is now of a consistency to admit of its being blown into a hollow globe, as exhibited in fig. 8. The globe, however, not being rendered sufficiently thin by this first distension, it is repeated until the vessel has assumed the dimensions required. In every case of blowing, the pressure of the breath must be continued upon the tube for a short while, to prevent the globe from collapsing, which would be the case were the confined air allowed to escape. The external pressure would be greater than the resistance offered from within. If it is required to elongate the globe, this may be effected by dexterously whirling it in a circular manner through the air. The crystal is now in a fit state for lying horizontally upon the chair arms, as shown in figs. 9 and 10. The chair arms are merely two pieces of wood lying parallel to each other upon the workman’s seat or chair. The arm which lies next the heated metal is protected from injury by being covered with an iron plate. Another instrument, called a punty or “pontil,” is employed. This is a solid iron rod of a cylindrical shape, and smaller and lighter than the hollow tube at first used. A small quantity of melted glass is collected upon one end of this by an assistant, and applied to the end of the globe, as shown in fig. 9. The two masses of glass are thus united together, and that attached to the hollow tube is easily separated from it by touching it near to where the tube enters the globe, with a small piece of iron wetted with water. By this means the glass cracks, and a smart blow upon the iron tube completes the disunion. The workman now takes the punty from his assistant, and laying it upon the chair arms, rolls it backwards and forwards with his left arm, whilst with his right he moulds it into the various shapes required, by means of a very few simple instruments. By one of these, called a procello, the blades of which are attached by an elastic bow, like a pair of sugar tongs, the dimensions of the vessel can be enlarged or contracted at pleasure. Any superfluous material is easily cut away by means of a pair of scissors, glass when red hot being very easily divided. For smoothing and equalizing the sides of the vessel, a piece of wood, generally cedar, is used; and the workman is also furnished with compasses and graduated scale, to ensure the regularity in shape and size required. The article being finished, is detached from the punty in the same way as formerly, and weighed in a pair of scales to see that there has been the proper quantity of glass consumed in its manufacture. It is then carried by means of a pronged stick to the annealing oven, or lier as it is technically called.

The process of annealing is one of the last importance; because, were glass not properly annealed, it would crack with even very slight changes of temperature; see the article ANNEALING in this work. Plate CCLXXI, fig. 3, represents an annealing oven. It is simply a long, low, rectangular chamber, heated at one end, and provided with various shallow iron trays, which can be passed along the bottom of the chamber. Upon these trays the manufactured goods are put; and the lier pans, as they are successively filled, are pushed towards the colder end of the oven, from whence they are taken in a state little warmer than the temperature of the external atmosphere.

Glass Cutting.—The cutting, or rather the grinding of crystal, forms a distinct business in a flint-glass-house. In the manufactory before alluded to, steam power is employed to give motion to the machinery by which the process of cutting is effected. A shaft proceeding from the engine causes the revolution of several large drums, which run along each side of the cutting room. Upon these drums belts run, which proceeding upwards, pass over smaller wheels (such as \(a\), fig. 4). By this means the cutting wheel \(b\) is made to revolve with great celerity. Opposite it the workman is placed, and applies to the surface of the wheel the article which is to be cut. Above the cutting wheel is a conical-shaped vessel \(c\), made of wood, and filled with fine sand, which being moistened with water, runs

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1 Dictionary of Chemistry, vol. i. p. 496. through upon the cutting wheel at the lower extremity, in regular discharge. The hole in the bottom is of such dimensions, and so situated, as to admit the escape of the exquisite quantity of moistened sand. Below the wheel is vessel, which receives the sand and water run down upon the wheel. Every one who has seen a crystal shop, must have remarked the infinitely varied appearances which the articles formed of flint-glass present. It is evident that, to produce these, the wheels must be of very various forms, broad, narrow, flat edged, mitre-edged, that is, having two faces, which form a sharp angle at their point of meeting, convex, concave, &c. They are made of iron both cast and malleable, of Yorkshire stone, and of willow wood. The iron wheels are used in the roughest part of the operations, and articles ground by these are further smoothed down by a wheel of Yorkshire stone. Wooden wheels are employed in the further smoothing and polishing of the crystal. For smoothing the surface, the edge of the wheel is dressed with either rotten stone or pumice stone; and for imparting to it the highest degree of polish, pumice powder is employed.

There are certain crystal shades in use for softening the light diffused by lamps. The process by which this lessening of the transparency is effected is called frosting. The roughness is imparted to the inner, not the outer surface of the vessel; and it is done by the former being fixed in a hole, and rubbed by a workman with a piece of wood covered with wet sand.

**BOTTLE-GLASS.**

Plate CCLXVIII. fig. 4, is a ground plan, showing all the necessary buildings for two bottle-houses, and in one of the houses the ground plan of a four-pot furnace and arches. The furnace is an oblong square, similar to what we have described the crown-furnace to be, but arches over in the barrel shape. It is erected in the centre of a brick cone, above a cave, which admits the atmosphere to the grating. The working holes of this furnace, opposite each pot, for putting in the materials and taking out the liquid glass, are each about one foot in diameter. At each angle of the furnace there is also a hole about the same size communicating with the calcining arch, and admitting the flame from the main furnace, which reverberates on and calcines the materials in the arch. Fig. 1 shows the main furnace; 2, 3, 4, 5, the ash arches for calcining the materials; 6, 7, 8, 9, 10, 11, annealing arches; 12, two-pot arches; 13, what is considered an improvement; 14, clay-house, for picking, grinding, sifting, and afterwards working the clay into paste for the purpose of manufacturing pots; 15, mill house for grinding clay; 16, building containing a calcareous furnace for experiments, for preparing the materials, when the ash arch attached to the main furnace is under repair, including, 1, a sand crib, and 2, an ash crib for sitting and mixing the materials, sufficient for two houses.

The common green or bottle glass is made of the coarsest materials; sand, lime, sometimes clay, any kind of alkali alkaline ashes, whose cheapness may recommend it to the manufacturer, and sometimes the vitreous slag produced from the fusion of iron ore. The mixture most commonly used is soap-maker's waste, in the proportion of three measures to one measure of sand. The green colour of the glass is occasioned by the existence of a portion of iron in the sand, and, it may be, also in the vegetable ashes which it is composed.

To distinguish it from flint-glass, which pays a higher duty, government does not allow the use of any but the nearest kind of sea or river sand. When castor oil or champagne bottles are wanted, a portion of crown-glass flint is added, to improve the colour. The impurity of the alkali, and the abundance of fluxing materials of an earthy nature, combined with the intense heat to which they are subjected, occasion the existence of but a very small proportion of real saline matter in the glass; and thereby render it better than flint-glass for holding fluids possessing corrosive properties.

The soap-maker's waste is generally calcined in two of the coarse arches, figs. 3 and 4, which are kept at a strong red heat from twenty-four to thirty hours, the time required to melt the materials and work them into glass, which is termed a journey. After the soap-maker's waste is taken out of the arch, it is ground and mixed with sand in the proportions already mentioned. This mixture is put into the fine arches, and again calcined during the working journey, which occupies about ten or twelve hours more. When the journey is over, the pots are again filled with the red-hot materials out of the fine calcining arch. Six hours are required to melt this additional quantity of materials. The pots are again filled up, and in about four hours this filling is also melted. The furnace is then kept at the highest possible degree of heat, and in the course of from twelve to sixteen hours, according as the experience of the founder may determine, the materials in the pots are formed into a liquid glass fit for making bottles. The furnace is now checked by closing the doors of the cave, and the metal cooling, it becomes more dense, and all the extraneous matter not formed into glass floats upon the top. Before beginning to work, this is skimmed off in the way already described in our account of crown-glass making. A sufficient quantity of coals is added at intervals, to keep the furnace at a working heat till the journey is finished.

After the pots have been skimmed, the person who begins the work is the gatherer, who, after heating the pipe, gathers on it a small quantity of metal. After allowing this to cool a little, he again gathers such a quantity as he conceives to be sufficient to make a bottle. This is then handed to the blower, who, while blowing through the tube, rolls the metal upon a stone, at the same time forming the neck of the bottle. He then puts the metal into a brass or cast-iron mould of the shape of the bottle wanted, and, continuing to blow through the tube, brings it to the desired form. The patent mould now in use is made of brass, the inside finely polished, divided into two pieces, which the workman, by pressing a spring with his foot, opens and shuts at pleasure. The blower then hands it to the finisher, who touches the neck of the bottle with a small piece of iron dipped in water, which cuts it completely off from the pipe. He next attaches the punty, which is a little metal gathered from the pot, to the bottom of the bottle, and thereby gives it the shape which it usually presents. This punty may be used for from eighteen to twenty-four dozen of bottles. It is occasionally dipped into sand to prevent its adhering to the bottle. The finisher then warms the bottle at the furnace, and taking out a small quantity of metal on what is termed a ring iron, he turns it once round the mouth, forming the ring seen at the mouth of bottles. He then employs a shears to give shape to the neck. One of the blades of this shears has a piece of brass in the centre, tapered like a common cork, which forms the inside mouth; to the other blade is attached a piece of brass, used to form the ring. The bottle is then lifted by the neck on a fork by a little fellow about ten years of age, and carried to the annealing arch, where the bottles are placed in bins above one another. This arch is kept a little below melting heat, till the whole quantity, which amounts to ten or twelve gross in each arch, is deposited, when the fire is allowed to die out.

Such is a brief view of the various methods of manufacturing glass. The physical properties of this useful sub- The manufacture of glass is subjected to the excise laws; and the duties are not only very heavy, but the regulations for levying them are most complex and oppressive. The injuries which are inflicted upon trade by such a system of taxation are strikingly exemplified in the case of glass. In 1794, when the duty was L.l., Is. 5d. per cwt. for plate and flint, the other kinds being taxed in proportion, the quantities paying duty were as follow: Flint and plate, 67,615 cwt.; broad, 20,607; crown, 83,940; bottle, 227,467. The duties were successively raised, until in 1813 they amounted to L.4. 18s. The result of this was, that in 1816 the consumption had declined to, plate, 29,600; broad, 6140; crown, 55,502; bottle, 155,595.

In 1825 the duty was reduced one half, and the consumption rose to about what it was in 1794. But since the wealth and population of the country have more than doubled since that period, and as general luxury has been greatly extended, the manufacture of glass ought to have been nearly trebled. This would certainly be the case were the duties lowered or abolished. The following accounts show the pernicious influence of the existing duties:

I.—Account of the number of Glass-Houses respectively employed in the Manufacture of Broad, Crown, Flint, Plate, and common Bottle Glass, in each year from 1829 to 1832 inclusive, in the United Kingdom.

| Years | Broad Glass | Crown | Flint | Plate | Common Bottle-Glass | |-------|-------------|-------|------|-------|-------------------| | 1829 | 2 | 28 | 54 | 3 | 42 | | 1830 | 2 | 25 | 54 | 2 | 39 | | 1831 | 2 | 24 | 55 | 2 | 36 | | 1832 | 2 | 28 | 59 | 2 | 39 |

II.—Account of the Quantities of Flint, Plate, Broad, Crown, and Bottle Glass, charged with the Duty in each year from 1829 to 1832 respectively, with the Rates of Excise Duty and Revenue accruing thereon.

| Years | Flint-Glass | Rate of Duty | Plate | Rate of Duty | Broad | Rate of Duty | Crown | Rate of Duty | Bottle-Glass | Rate of Duty | Gross Duty | Drawback | Revenue | |-------|-------------|--------------|-------|--------------|-------|--------------|-------|--------------|-------------|--------------|-----------|----------|---------| | 1829 | Cwt. | s. | Cwt. | s. | Cwt. | s. | Cwt. | s. | Cwt. | s. | L. t. d. | L. t. d. | L. t. d. | | | 79,250 | 56 | 14,484| 60 | 6,864 | 30 | 114,862| 73 | 382,894 | 7 | 831,809 | 18 10 | 224,794 | 17 2 | 607,015 | 1 8 | | 1830 | 72,942 | 13,301 | 4,845 | 63 | 96,555| 340,793 | 725,597| 1 3 | 182,678 | 4 | 542,918 | 16 7 | | | | | 1831 | 75,619 | 15,067 | 5,915 | 64 | 100,086| 293,868 | 736,512| 0 1 | 204,152 | 2 | 532,359 | 18 1 | | | | | 1832 | 75,771 | 12,270 | 5,304 | 63 | 103,902| 316,365 | 748,097| 3 11 | 189,565 | 7 | 558,531 | 16 3 | | | |

III.—Account of the Quantities of British-made Glass retained for Home Consumption, with the Imports of Foreign Glass entered for Home Consumption; the Amount of Customs-Duty on the latter, and the Nett Revenue arising from British Glass, in each year from 1829 to 1832 both inclusive.

| Years | Flint | Plate | Broad | Crown | Bottle | Plate | Crown | Bottle | Revenue on Foreign Glass | Nett Revenue on British Glass | |-------|-------|-------|-------|-------|--------|-------|-------|--------|--------------------------|----------------------------| | 1829 | 49,004| 14,299| 6,864 | 97,134| 209,862| 1,763 | 152 | 764,778| 16,708 | 610,307 | | 1830 | 48,063| 13,057| 4,845 | 84,178| 163,549| 1,436 | 104 | 743,768| 16,411 | 526,507 | | 1831 | 48,887| 14,796| 5,915 | 83,527| 143,989| 863 | 104 | 693,454| 15,841 | 516,518 | | 1832 | 49,552| 11,990| 5,304 | 90,253| 151,705| 717 | 25 | 645,526| 14,532 | 543,999 |

We can only notice a few of the regulations as to the manufacture of glass. Every glass-maker must take out an annual license, which costs him L.20 for each glass-house; and he must make entry at the next excise-office, of all work-houses, furnaces, pots, pot-chambers, annealing arches, warehouses, and the like, under a penalty of L.200. Previously to the charging of the pots, twelve hours' notice must be given in writing, of the time of beginning, the weight of metal, and the species of glass, on pain of L.50. If any material or preparation be put into a pot after notice has been given and a gauge taken by the officer, penalty of L.50 is incurred; and if the manufacture be of flint-glass, the penalty is L.200. The officers are allowed to have access to the works at all hours by day and night, any attempt to obstruct them incurring a penalty of L.200; and the counterfeiting, altering, or effacing any marks made by them being visited with a penalty of L.500; connivance at its being done subjects the aggressor to a fine of L.200. The whole of the metal intended to be manufactured into common-glass bottles is to be worked within sixteen hours next after the same shall be begun; and when the bottles are put into the annealing arches, manufacturers are then, in the presence of the officer, to charge the pots with fresh materials, other than broken glass, not less than fifty pounds weight; and declarations are to be delivered in writing, of the number of such bottles, on penalty of L.100. Fraudulent weighing of glass is visited with a heavy penalty. Notices are not to be given for drawing out bottles, but only between eight o'clock in the morning and six o'clock in the afternoon. No crown-glass, German sheet-glass, or broad window-glass, can be manufactured beyond the thickness of one-ninth part of an inch, without being subjected to the duty paid on plate-glass. Such are a few of the laws and regulations, alike vexatious and impolitic, which have retarded the progress of glass-making, and that too at a time when almost every other species of manufacture had far more than doubled itself. In fact, from the making of the pots themselves to the packing up of the glass for sale, every thing is done after a certain manner, which is determined by act of parliament. This being the case, how improvements are to be made in the art it is difficult to conceive. The laws which regulate the packing and exportation of glass are equally burdensome with those relative to its manufacture. The amount of drawback allowed upon this article will be seen from the table above given. Engraving on Glass. Professor Beckmann has proved, at as early as the year 1670, the art of etching upon glass was discovered by Henry Schwanhard, son of George Schwanhard, who was a celebrated glass-cutter, patronised by the Emperor Ferdinand III., about the middle of the last century. At the time of his death, 1697, the father practised his art at Prague and Ratisbon. Whether the son followed the same business at the same towns, or moved to Nuremberg, is not very evident; but in the year above mentioned, some aqua-regia (nitro-muriatic acid) having accidentally fallen on his spectacles, he was surprised to find the glass corroded by it, and become quite soft. He thus, it is said, found himself in possession of a liquid by which he could etch writing and figures on plates of glass.

But it is probable, as Beckmann seems to think, that he had discovered the fluoric acid itself; for in the year 1725 there appeared in a periodical work the following receipt for making a powerful acid, by which figures of every kind can be etched upon glass.

"When the spiritus nitri per distillationem has passed to the recipient, ply it with a strong fire, and when well phlegmated, pour it, as it corrodes ordinary glass, into Weldenberg flask. Then throw into it a pulverised green Bohemian emerald, otherwise called heosphorus (which, when reduced to powder, and heated, emits in the dark a green light), and place it in warm sand for twenty-four hours. Take a piece of glass well cleaned, and freed from grease by means of a ley; put a border of wax round about an inch in height, and cover it all over with the ore acid. The longer you let it stand so much the better; and at the end of some time the glass will be corroded, and the figures which have been traced out with sulphur and varnish will appear as if raised above the pane glass."

That the Bohemian emerald, or heosphorus, mentioned in this receipt, is green sparry fluor, cannot, says the professor, be doubted; and he seems to have as little doubt of the receipt itself having passed from Schwanhard and his followers to the periodical work of 1725, from which it was inserted in the Oekonomische Encyclopädie of Krunitz. His supposition certainly acquires a considerable degree of probability from the similarity of Schwanhard's method of etching to that which is here recommended, and which is so different from what is now followed. At present the glass is covered with a varnish either of isinglass dissolved in water, or of turpentine oil mixed with a little white lead, through which the figures to be etched are traced on copper; but Schwanhard, when he had drawn his figures, covered them with varnish, and then by his liquid corroded the glass around them. His figures, therefore, when the varnish was removed, remained smooth and clear, appearing raised from a dim or dark ground; and Beckmann, who had persuaded some ingenious artists to make trial of this ancient method of etching, declares that such figures have a much better effect than those which are cut into the glass.

Burning Glass. See Burning Glass. Weather Glass. See Barometer. Musical Glasses. See Harmonica. Looking Glasses. See Mirror.