COLLIERY

Colliery. A COLLIERY is a place where coal is found in stratified masses, and excavated by manual labour, and commonly brought to the surface by mechanical power.

The exact date when coal began to be used as a fuel is very uncertain; the appearance, if not the use of the mineral, must have been known for a long time in districts where the deposit was naturally exposed; and, according to some authorities, it is mentioned as having been used in England in the ninth century, 852. In 1259 King Henry III. granted the privilege of digging coals to certain parties in Newcastle. Seven years afterwards coal had become an article of export, and was termed sea-coal; and in 1306, so extensive was the use of coals in London, that parliament complained to the king of the noxious vapours therefrom polluting the atmosphere. In consequence of which proclamation was made against their further use, lest the health of the knights of the shire should suffer during their residence in the metropolis.

Blythe, writing in 1619, states, "It was not many years since the famous city of London petitioned the parliament of England against two nuisances or offensive commodities, which were likely to come into great use and esteem; and that was, Newcastle coals, in regard of their stench, &c.; and hops, in regard they would spoil the taste of drink, and endanger the people."

In Belgium the earliest reference to coal was in 1198 or 1200 in the country of Liège, where, according to tradition, a blacksmith was the first to use it as fuel.

In France the precise period of its adoption as a substitute for wood is not ascertained. The commencement of its use in Paris was in 1520, the coal being drawn, not from the mines of France, but from the collieries of Newcastle.

In Scotland coal was known and used probably at a very early date. We are informed by Chalmers, the antiquarian, that coal was worked at Bo'ness by William de Verepont before the end of the twelfth century, and that a tenth of the coals was paid to the monks of Holyrood House.

It is more curious, however, than important here, to trace the date when mineral coal was first used as a fuel. The earliest employment of it in England in the manufacture of iron was in 1713 at Colebrookdale, in Scotland about the commencement of the eighteenth century, and in France in 1782.

Distribution. On examining a geological map of the world, it is interesting to compare the known mineral resources, and their distribution throughout the different countries, in strata of every variety of depth and area; and how remarkable that these productions (though extensively distributed) should be principally confined to those countries where the inhabitants, possessing the advantages of civilization, are enabled to make them contribute to the comfort of the great human family. See page 127.

Geological position. The stratified matter which composes part of the crust of the earth is deposited in beds or layers. Geologists have very satisfactorily shown the order in which the various layers have been deposited. "Had these lain in regular undisturbed succession, man would have made but little progress in deciphering their history, as the greatest perpendicular descent man has yet made into the crust of the earth does not extend to half a mile. But as these rocks are thrown up into slanting and irregular positions, so that the lowest are brought to the surface equally with the most recently formed, geologists have been able to collect a regular series of stratified rocks from those disposed as it were but yesterday, to the unstratified granite which forms their basis."

The following figure (No. 1) will give an idea of the stratified rocks as they occur in Britain:—

The figure is a vertical geological cross-section of the British Isles. On the left, the strata are grouped into four main periods: TERTIARY, SECONDARY FORMATION, TRANSITION, and PRIMARY. Below these is a layer labeled GRANITE. The strata are represented by horizontal bands with different patterns. The TERTIARY section includes 'Sandstone, Marls, and Plastic Clay'. The SECONDARY FORMATION section includes 'Chalk and Lias formation', 'New Red Sandstone And Magnesian Lime', 'Coal measures', and 'Mountain Limestone'. The TRANSITION section includes 'Old Red Sandstone, Silurian Limestones, and Sandy Slates'. The PRIMARY section includes 'Clay Slates, Mica and Tale Schists, Gneiss rocks'. On the right, a small sketch shows a landscape with trees and a building, indicating the surface level.

Coal is found in those strata designated the secondary formation, or coal measures, and in seams varying from an inch to forty feet; and though great sameness is observable in the continuous thickness and quality of each seam, still irregularities are of frequent occurrence, and of sufficient extent to baffle the profitable working of many well laid out collieries.

The irregularities common to all coal-fields are as follows: nips or weants, shaken coal, saddle-backs, baulks, pot-ties, bottoms, gaves, hitches, and dikes.

Nips or weants. The coal is said to be "nipped" out when Nips. the roof and pavement approach each other, thereby reducing the thickness of the seam. It generally happens that this irregularity is more fully developed where the roof is hard—for example, where a considerable thickness of sandstone is in near or immediate contact with the coal. The general appearance of a seam of coal thus troubled is represented by figure 2.

The diagram shows a cross-section of a coal seam. The top layer is labeled 'roof' and the bottom layer is labeled 'pavement'. The coal seam between them is irregular, with some parts being very thin and others very thick. Points A, B, and C are marked on the diagram. A is at the top of the roof, B is at the bottom of the pavement, and C is at the side of the seam.

Referring to it, A is the roof; B the pavement; and CC the average thickness of the seam. Practical men are of opinion that this description of irregularity does not lessen the seam of coal; that is, when the thick and the thin parts are added together, they will nearly form an equivalent to the known average of the seam; and when this is not the case, the coal is found in a more compact state.

Colliery. Shaken coal is frequently found in the neighbourhood of "wants," in a regular and seemingly untroubled state; the seam is seldom changed in thickness, but the coal is no better than a heap of dross or small coal; and may be shovelled from the seam as off a coal-hill. The pavement is generally wet and soft. There is considerable diversity of opinion regarding the cause likely to have produced this change; and it is not unlikely to suppose that a stratum of mud or gravel may be in immediate connection, and not far distant from the pavement, which, when acted upon by pressure, would crush an inelastic substance like coal, and thus account for the change.

Saddle-backs, pot-bottoms, or baulks, and gaws, are local terms given to irregularities in the roof or pavement of coal; when they occur on the pavement, it may be ascribed to the inequality of the surface on which the original deposition of vegetable matter (from which coal has been transmuted) was laid; but when found on the roof, may be supposed to have been occasioned by interruptions to these deposits or uneven pressure. The following is an illustration of these irregularities as they are met with in mining, figure 3:—

A, a saddle-back; B, a baulk or pot-bottom; C, a gaw; and DD the seam of coal. Gaws are most frequent, and generally lie in a level-course direction; they are the reverse of saddle-backs, and as distinguished here they both represent changes of level in the pavement of the seam.

Hitches are dislocations, and show that the seams of coal and accompanying strata, though continuous at a former period, have been torn asunder by violent action, and their continuous regularity of level and inclination changed, the strata on the one side of the fracture being depressed, or on the other elevated. These subsidences or upheavals occur in almost every direction, from an inch to 1800 feet (as has been proved to the south of Glasgow); they follow one general law—that is, the fissure is always at a certain angle to or from the point of contact with the section of the strata, and rarely perpendicular. The accompanying section, fig. 4, represents a seam of coal k, being worked to-

wards m, interrupted by hitches—A being an upthrow and B a downtthrow.

When the strata are upheaved or elevated, the angle of the fissure is in the direction of AC; when depressed or thrown down, it lies in the direction of BD.

It has often been matter of surprise to those engaged in mining that so little is visible on the surface to indicate the place of these dislocations. It might have been expected

that the displaced strata would have been found in the position of the dotted lines eee in a protuberance at the surface; but such is not the case; and in inquiring by what agency this elevated mass has been denuded and the present level produced, we are forced to take into account the slow operation of natural causes, extending over such a lengthened period of time, that we have no data by which to estimate it; and yet the time required for the abrasion of these elevations sinks into insignificance, when compared with that required for the degradation of previously indurated matter, of which the stratified rocks (upwards of eight miles in thickness) are composed.

Dykes form interruptions in the strata, but seldom Dykes. cause any alteration of level or inclination. When composed of trap, they can generally be traced through a considerable extent of country. Their volcanic origin is undoubted, and the remains leave unmistakable proof of their ancient connection. Section fig. 5 will give a general idea of the manner in which coal-beds are sometimes deranged by this description of trouble.

BB, the dyke; aaaa, branches, or beds injected into the surrounding strata, irregular, but sometimes parallel with the stratification for a considerable distance; and when one of these follows the course of a seam of coal, it (the coal) is either displaced or reduced to cinder.

Clay dykes are frequently encountered from ten to thirty fathoms from the surface. They form a complete barrier like dykes of trap, but do not alter the quality of the coal; and though not traceable for a great distance, they often extend to many yards in thickness.

Inclination scarcely comes under the head of irregularities; and though some seams are unworkable to profit on account of their rapid inclination, all coal-seams lie more or less at an angle to the horizon, and are never found truly level. Taylor, in his statistics of coal, when referring to the irregularity of inclination and out-crop, explains,—"During our investigations, we have remarked that the true positions of those veins which had their bassets on the slopes of the mountains were in most cases rendered obscure by the curvature of the crops almost at right angles to the true inclination of the veins. We ascribe this to the atmospheric agency operating to a given depth below the surface, and to the mechanical influence of surface waters, decomposition, the sliding down of the higher masses, &c. In every instance which has come under our observation, in relation to the out-cropping of coal seams on these slopes, we have perceived the manifestation of the like influences which have deflected the 'wash,' or decomposed materials of the coal veins from their true courses, and thrown them over among the alluvial detritus, generally in a curve, as shown by the next figure, No. 6, which is merely the representative of numerous corresponding cases."

Though it is universally admitted that all coal-seams are the Varieties result principally of accumulations of vegetable matter under different circumstances or degrees of pressure, it is evident that local or other causes have tended materially to

Colliery. change their quality. If we take the seams known to exist in one of our great coal-fields, and compare them, we find a marked difference in the quality of each; and the quality is not only different, but the structure, analysis, general appearance, and also the uses to which they are applied.

The varieties of coal commonly known and generally in use throughout Great Britain, are cubical coal, fat bituminous coal, anthracite, steam-coal, and cannel coal.

Cubical coal. Cubical or dry coal is dark and shining; when worked, it admits of being put out in large masses; it has general properties in common with all seams of coal, viz., it is essentially composed of carbon, oxygen, hydrogen, and nitrogen. The quality of coal depends upon the relative proportion of these ingredients.

The term dry coal has sometimes also been applied to coal of this description in contradistinction to those which cake or cement. It burns freely, with much flame and heat. The "splint coal" of Scotland, famous for smelting ores in the blast-furnace, is of this class; and though other coals have become greater favourites in the parlour, none have yet been found equal to it for use in the blast-furnace; and it is a gratifying reflection for those engaged in the iron trade in Scotland, that vast fields of it still remain to be worked.

Fat bituminous coal. Fat bituminous or caking coals differ little in appearance from the open burning cubical dry coal; when exposed to a high temperature they swell considerably, and during combustion have a direct tendency to cake or cement, but though well adapted for household use, their cementing property has hitherto proved objectionable to their being used in the blast-furnace in a raw state.

Anthracite coal. Anthracite coal is black, brittle, and highly lustrous. When subjected to a high temperature it ignites, burns with considerable heat, produces no smoke, and leaves a small percentage of ash. It is extensively diffused throughout Wales; vast tracts of it exist in America. It also abounds in Ireland, known by the name of Kilkenny coal, and in Scotland as blind coal, where it is much prized by maltsters, brewers, and millers, on account of its being free of smoke during combustion, and possessed of strong heating powers. Of late years anthracite has been introduced successfully in the blast-furnace, partly in England, but extensively in America. The following table exhibits the amount of carbon contained in samples of this mineral from all the principal known deposits:

Steam-coal. Steam-coal is a species of the above-described, and sometimes termed "smithy coal." It is neither bituminous nor anthracite; it possesses more hydrogen than the latter, and more carbon than the former. It has generally a clear glancing appearance, is somewhat tender, ignites easily, gives off comparatively little smoke during the process of combustion, and is now generally known as steam-coal, for which purpose it is highly prized.

At one time it was considered that coal of this descrip-

tion had been deprived of its volatile property, from contact with particular strata. It is now clearly established (particularly in Scotland), that wherever coal of this quality is found, it is close to, or in the immediate neighbourhood of trap (whin); and since the increased demand for steamboat coal, coal-fields have been taken for this description of coal, with no other direct knowledge of its existence, than that the trap lay at a given distance from the position of the coal-seams. It is proper to remark, that when freestone intervenes between the trap and the coal, it approaches nearer to the anthracite than when separated by fire-clay or shale. In some districts the coal is found excellent in quality from 15 to 30 fathoms beneath the trap. It is unnecessary here to remark, that where the trap does not exist, the coal is of the common open burning bituminous nature, and when in close contact it is either anthracite or cinder coal.

Cannel or gas coal is of a grayish-black, or dark brown colour, and may be termed non-lustrous. It is variable in gas coal quality, but uniform in stratification, and may be seen in a short distance blending into a great variety of shades; and not unfrequently its character is changed into blackband ironstone, or bituminous coal. It is extensively worked in the Lancashire coal-field, near Wigan; and there are various seams of it in the upper and lower series of the Scottish coal-field, the Torbanehill being the most valuable in the former, and the Lexmahoy in the latter. Cannel is of less specific gravity than common "cubical coal;" it is very compact, ignites with great facility, and burns with a brilliant flame. It has long been customary throughout Scotland for farmers to lay in a stock of it for the winter, on account of its light as a substitute for candles, hence the name cannel coal. It first received its name in Lancashire, where the word candle is commonly pronounced cannel by the peasantry.

It is now mostly used in producing gas, for which purpose it is admirably adapted.

Before proceeding to describe the searching for and working of coal-fields, it may be proper to advert shortly to the general mode of letting them. The arrangements are various in detail; the adventurer or tenant agrees to pay a certain value or royalty for the coal he proposes to work—in general, at either so much per ton or acre, or percentage upon the sales at the pit mouth. Coupled with the royalty there is a sum fixed as rent, which makes it imperative on the part of the tenant either to work the coal to a given extent, or pay for the occupation of the ground. The sum fixed is generally sufficient to induce the tenant to work the field, or otherwise show cause for abandoning it.

Prior to the introduction of the science of geology, the definite character and extent of the strata which contain the coal measures seem to have been imperfectly understood. But it is to that science we are indebted for our information regarding those deposits, the importance of which is admitted, when it is considered that this formation is upwards of one and a half mile in thickness, composed of hundreds of layers, and often difficult to distinguish from the masses of stratified matter in immediate connection.

The geological arrangement marks with precision the upper and the lower link of connection, the new red sandstone on the one side, and the mountain limestone on the other. Without a knowledge of this general arrangement, it is obvious that the exploring miner in past times (however intelligent otherwise) must have frequently felt perplexed; and the course then pursued yet finds an occasional advocate, viz., that coal is to be got anywhere by only sinking deep enough. But we now know the limit of the coal measures and their general construction; and it is not assumption to say, that a successful search for coal is not altogether a matter of chance; and though we find sometimes in our researches that certain divisions of strata are absent, their stratigraphical order is never subverted, that is, the new red sandstone may repose upon the mountain lime, or

Colliery. old red sandstone, but never upon the chalk and lias formation.

It may not be out of place to advert to the variability of the vegetable deposits throughout mining districts, and the advantage of being well informed regarding the leading features that serve to distinguish all coal-fields. The most marked and continuous of these are, seams of limestone, mussel-bands, and thick deposits of sandstone; seams of coal and ironstone vary much, and often cannot be recognised at another point of the same field; therefore as individual seams they are not to be trusted as guides, unless in close connection with those known groups to which they belong.

The search so long as it is confined to the coal measures, is comparatively easy; but in exploring fields that are distant from mining operations, and where no trace of the coal measures are found from the intervention of superior strata, it is then necessary to act with caution. Not that geologists have misnamed or misplaced the chalk or lias formation, nor that they do not exist often many hundred fathoms above the coal measures, but that frequently they are found overlying the outcrop of older formations (unconformably), and comparatively thin, as shown by figure 7.

When this irregularity of deposit comes to be generally understood, the explorations of the miner will take a wider range than they have hitherto done, and in some unpromising situations important discoveries may yet be made.

In searching for minerals, it seldom occurs that enough of the strata is exposed to warrant a shaft being put down; and it generally happens that the preliminary expedient of boring is had recourse to, as being the most expeditious and least expensive mode of ascertaining the character and contents of any mineral field.

The process of boring is well known, and has already been described under the head BLASTING. When the term is used in connection with mining, it is understood that a hole is to be drilled or bored into the earth. This is done by a chisel of an indefinite length, sometimes 20 feet and sometimes 1200 (according to the depth of the bore), the continuous length of which is formed by pieces of iron 9 feet long (or any other convenient length), with a screw on each end termed male and female.

The chisel at first, and for a number of fathoms, is lifted by the hands until the weight becomes inconvenient to lift directly, when a lever of the first power is introduced: the chisel or rod is suspended from the end of it, and the workmen exert their power at the other, while the person in charge turns the chisel by a cross piece of wood termed the brace head, attached to it. The process of cutting is thus performed by raising the chisel, turning it, and allowing it to fall by its own gravity; and the strata cut is procured by introducing for the lowest division of the chisel, a hollow tube with a valve in the bottom—when it is forced down into the bore the valve opens and receives the detritus produced by the action of the chisel, which, when brought to the surface is washed and preserved in samples, and delivered by the borer to his employer, in proof of the journal he renders.

To perform this description of work well, great care and attention is required; and though there are frequent failures, it may be remarked that a skilful workman renders a very correct description of the strata he bores through; and, generally, from a few well-selected bores, a good general idea can be formed of a field, and what it contains.

Plate CLXXV. fig. 3, will illustrate the principle of prov-

ing a mineral field by boring. Referring to it, the figure represents a line direct from the dip to the rise of the field, and the inclination of the strata is one in eight. No. 1 bore is commenced at the dip, and reaches a seam of coal A, at 40 fathoms; at this depth it is considered proper to remove farther to the outcrop, so that inferior strata may be bored into at a less depth, and a second bore is commenced. To find the position of No. 2, so as to form a continuous section, it is necessary to reckon the inclination of the strata, which is 1 in 8; and as bore No. 1 was 40 fathoms in depth, we multiply the depth by the rate of inclination, $40\; \backslash times\; 8\; =\; 320$ fathoms, which gives the point at which the coal seam A should reach the surface. But there is generally a certain depth of alluvial cover which requires to be deducted, and which we call 3 fathoms, then $40\; -\; 3\; =\; 37\; \backslash times\; 8\; =\; 296$ fathoms; or say 286 fathoms is the distance that the second bore should be placed to the rise of the first, so as to have for certain the seam of coal A in clear connection with the seam of coal B. In boring, sometimes the miner gets bewildered; as will appear if we trace the course of bore No. 3, where the seam B, according to the same system of arrangement should have been found at or near the surface; instead of which another seam C is proved at a considerable depth, differing in character and thickness from either of the preceding. This derangement being carefully noted, another bore to the outcrop on the same principle is put down for the purpose of proving the seam C; the nature of the strata at first is found to agree with the latter part of that bored through in No. 3, but immediately on crossing the dislocation at A it is changed, and deeper the seam D is found.

A skilful borer in such a situation would be aware, that in both of these cases (3 and 4) there must be some material derangement; and by changing his position to the dip or outcrop, would rarely fail in proving to a certain extent the derangement and the cause, thus forming one of the most important operations connected with economical mining.

Having proved a field by boring, the next important step is to fix on an eligible situation for a "winning."

A coal-field is said to be "win" when access is made to the seams of coal. This may be done either by a vertical shaft or a crosscut mine. The accompanying figure, No. 8, will illustrate both: A B being a crosscut mine, by which the seams of coal 1 and 2 are win, and C D a vertical shaft by which the seams 1, 2, and 3 are win. When the field is

win by the former method, the coal is said to be level-free; if by the latter, not level-free. All coal situated above the level of the sea may be said to lie level-free, that is, if a level mine were continued from the surface of the sea throughout a district of country, all above the point of intersection would necessarily be drained. Sometimes from the contour of a country, rivers or valleys form natural mines, into which the drainage of coal seams may be economically taken. Ancient miners, for want of sufficient power to unwater their operations, were necessarily limited as to depth; to them a seam of coal level-free was of the utmost importance; to this their search was chiefly directed; and thus we find the sites selected for their operations were, generally speaking, level-free, or otherwise easy of access. Now that we have an unlimited power in the steam engine, seams of

coal are got by shafts varying from 10 to 300 fathoms in depth; and though the latter is, perhaps, the greatest vertical depth to which the miner has yet pushed his operations in Great Britain, it by no means follows that that is the limit; for at no distant period future generations must, in some situations, draw their mineral supplies from shafts compared with which the latter will appear of insignificant depth.

Among the various forms of shafts, there are oval, circular, square, and oblong. The most common of these is the circular or oblong. When the surface is compact, the circular or oblong form may be adopted at pleasure; where the surface is deep and composed of mud, or sand charged with water, the circular form is generally adopted, as being the most nearly perfect form for resisting a uniform pressure. It is also the most suitable form for admitting of tubbing, a process of stopping back water much in use at deep collieries, and nowhere carried to such perfection as in the north of England. When first introduced it was effected by wood; at a later period iron cylinders were employed, cast in segments, made to rest upon each other; the joints, both upright and horizontal, being made tight with a layer of thin wood. A wedging crib was fixed at the bottom, and the segments were built up regularly to the height required. Where the layers in a shaft are so situated as to form a continuous drainage from rivers, or other regular sources, such a precaution for damming back water is of incalculable benefit, and should be taken advantage of at almost any cost. Tubbing, however, can only be effectively carried out under certain circumstances, and where the system of working does not interfere with the stability of the overlying strata.

To enter into the subject of sinking in detail, or to explain with any degree of minuteness the usual and necessary preparations and appliances, would swell this article far beyond the allotted space.

In general when a field has been proved to be free of insurmountable troubles or dislocations, and the whole of it can be drained by a dip-shaft, the most eligible situation for it is at the extreme dip of the field; by that arrangement any shafts sunk to the rise are dry; working upon the reverse system, that is, beginning with the first shaft near the outcrop, and in succession going to the dip, would lay the adventurer under the necessity of making erections for drawing water at the whole of them. However, there are many fields so situated by known dislocations, that to go to the dip of the field with the first shaft would be of very little advantage to after sinkings.

Sinking in many situations is difficult, and the laying out of a new colliery is a serious undertaking. The depth and nature of the alluvial cover to the rock strata, the weight of water to contend with, engine power, arrangements for future ventilation, besides many local difficulties for which no rule can be applied, are all points requiring the greatest deliberation and forethought. And when we consider that the deepest shaft in Great Britain was sunk and fitted up with engine power, &c., at an outlay of £1,000,000, extending over a period of ten years, we will then be able to form an idea of the cost and time generally required for such operations, however simple.

Having fixed upon the form of shaft, and the sinking through the surface having been secured either by timber, masonry, or tubbing, the operation of sinking by blasting is commenced. This work is performed by a class of men called sinkers, who are rather better paid than miners. The work, though disagreeable and dangerous, is generally preferred to mining. The tools used are similar to those in use at quarries. Latterly the galvanic battery has been introduced in the process of blasting; and thus a number of charges can be fired at the same instant, and to better purpose than by the common method. See BLASTING.

In sinking where the alluvial cover is soft, temporary

erections for lifting or pumping water are made until the rock strata be reached, and the shaft carefully secured. When the surface is of the usual compact nature, fittings may be put up at once.

For want of sufficient data, there is often considerable difficulty in deciding upon the amount of engine power required to drain a new field; some approximate idea may be formed from bores, but even under the most favourable circumstances there is uncertainty.

Plate CLXXXVI. shows two illustrations of pumping machinery, generally in use throughout the mining districts. Fig. 1 is the Cornish method of pumping by force pumps, direct from the main beam of the engine; and fig. 2, the common lifting pump with bell cranks connected by gearing to the engine shaft.

The Cornish system is common where heavy permanent fittings are made, and is then supposed to possess advantages over all others. The rods are constructed so as slightly to exceed the weight of the water, the power of the engine being applied to lift the rods, which, in descending by their own gravity, cause the ascent of the water. This method admits of the steam being used expansively.

The advantages claimed for the lifting pumps with bell-cranks are, their simplicity, and the reduced speed which can be obtained by means of gearing; for while the engine may be driven 300 feet a minute, the bell-cranks may travel at one-third of that rate.

When force pumps are introduced, it is generally after the pit is sunk, the lifting ones being better adapted for sinking with. When a shaft exceeds 45 fathoms in depth, there is generally more than one lift of pumps, and it is always considered sound economy not to exceed 35 fathoms with each lift. When they exceed this depth the tear and wear of the machinery is greater; besides, there is often water in the strata, which can be arrested at the lodgments connected with these lifts.

Referring to the plan of forcing pumps, fig. 1, a is the main beam; b the main rod reaching to the lowest plunger; c the working barrel fitted with stuffing box e; ff clack and door pieces; s suction; p pipes; l landing box by which the water is discharged into the lodgment m; n a dam formed of two divisions of plank let into the wall on each side, the space between the planking being filled with clay; s² the suction of the top set; d² the working barrel; e² the plunger glanded on the main rod b at r; h h clack and door pieces; p² pipes; l² the landing box which delivers the water at the surface.

In the plan of lifting pumps, fig. 2, a a the bell-cranks, b b the rods, c c the working barrels, ff clack pieces and doors, h h bucket doors, k k the suctions, m m the pipes, n n the landing boxes delivering the water at the surface, p p p rackings for keeping the pipes in a stationary position, and r the rod that connects the bell-cranks and engine.

During sinking a partial ventilation is required in the shaft, to carry off the gases and products of combustion. This is generally accomplished by temporary brattice or mid-wall. When the sinking has reached from 30 to 40 fathoms from the surface, the pumps, which hitherto may have been lowered as the sinking progressed, are fixed, and a lodgment is driven into the side of the shaft, for the purpose of collecting the water above it, and also to hold the discharge of the second lift of pipes which is now put on to follow the sinking of the shaft.

At a similar distance (should the sinking not have been completed) a second lift is fixed in the same manner, and a third column follows the sinkers, and so on.

It often happens that thin seams of coal are found conveniently situated in which these lodgments can be economically made.

The difficulties attending a dry sinking are few compared with one where there is much water to contend with; and in

Colliery. such cases, unless the engine power, pumping materials, crabs, cranes, and other tackling, are all kept in good repair the work will not go on; but with all these precautions difficulties occur where least expected, often causing extra expense and loss of time.

Preparatory operations to working. When the shaft is sunk and fitted up with guides for the cages, midwalls secured, and pumping operations complete, the next work is to lay out the pit-bottom arrangements. This generally embraces driving lodgment levels, erecting ventilating furnaces, and forming proper supports for the shaft.

Lodgment. The term lodgment is applied to the openings to the dip of the dip-head levels. These are formed to contain the water anticipated from the drainage of the mine in a given time: they require to be frequently attended to, otherwise the advantages to be derived from them will be very much nullified by the sedimentary deposit constantly accumulating in such a situation.

Levels. The term dip-head (sometimes pit-bottom) levels, means openings driven from the bottom of the shaft in a true level-course direction. Owing to the irregularity of the pavement, these openings seldom run in a straight line; their course is wholly guided by a flow of water to a given depth along the dip-side. It is of much importance to have them truly level: they form passages for the drainage to the lodgment, but when injudiciously made, curtail the limit of what would otherwise have been level-free coal.

Pit-bottom stoops. Pit-bottom stoops are extensive pillars of coal designed to secure the shaft and machinery. To proportion these correctly, the depth and quality of the overlying strata require to be carefully considered; but as this coal may be worked out at any subsequent period, the propriety of making ample provision for the security of the shaft at the outset will be apparent.

Working the coal. When the preliminary operations are completed, one or other of the numerous modes of working is adopted. At this stage of progress real skill and experience is invaluable, as frequently an injudicious arrangement of working has thwarted the success of an enterprise that otherwise might have been a profitable one.

It will appear obvious that, but for the inequality of cost in production, the best method of working a seam of coal is the one by which the greatest quantity of the mineral can be taken from a given area; but the difference of expenditure is frequently considerable, and hence a reason for varied modes of working. Still those different systems, however unlike they may at first appear, may very easily be shown to be represented by two distinct methods only, viz., those of pillar working and longwall.

To illustrate these varieties, see plan of the latter, and plans showing modifications of the former.

Longwall method. Plate CLXXV, fig. 1, shows the longwall method of working coal. In well regulated collieries where this system is practised, there are three winning-out walls, viz., the dip-head levels AA, and headway B. When these are kept going in a proper manner (a little in advance), the intervening workings may be compared to the excavation of a large intersected block of coal; the arrangement precludes the necessity of vertical cuttings ("shearing"), consequently saves labour, and produces a large proportion of round coal. The simplicity of this method, when compared with "pillar working" under any form, is very apparent. Colliers trained to it do their work with comparative ease; they arrange their operations so as to undermine or "hole" the coal (as at C, fig. 2) along their wall on the after part of the day, leaving it to be acted upon during the night by the overlying strata, which being only partially supported by the buildings, forces away the undermined portion of the coal before the workmen return. In the event of this failing, the coal is taken down with very little trouble by wedges, broken up, and sent away as sketched in fig. 2. Where

the work is kept advancing regularly, the roof does not break readily along the face of the coal. The same figure (No. 2) shows the order of the subsidence of the roof along the drawing roads.

When the "waste" is "stowed" in an average manner, the roof subsides from a half to two-thirds of the thickness of the seam; and the subsidence is generally complete (the roof at rest) at from 30 to 50 yards back from the face of the coal. When a "falling" intervenes between the coal and the roof, as shown at fig. 2, the colliers support it with wood for their own safety; another class of workmen (termed "brushers") take it down at night, and as much more of the roof as may be required for height of roadway; and with this they form the roadways, or make other requisite buildings along the wall-faces.

Plate CLXXVII, fig. 1, represents one of the most ancient methods of coal-working, known in Scotland as "stoop and room." By this system all the coal is taken away, except what is left for the support of the roof, which in general ranges from a fourth to a fifth of the whole. Fig. 2 illustrates a system of working, combining pillar and longwall, differing from the latter in the manner in which the roads are arranged and maintained, and from the former in the peculiar way in which the coal is extracted, and the roof supported. It is practised in the Yorkshire coal-field, and sometimes in Scotland.

Plate CLXXVIII, shows the mode of working coal by Newcastle bord and pillar, or what is more generally understood method; by the Newcastle method. It was formerly the practice, under this system, to remove the pillars subsequently to the excavations in the solid. An improved method is now introduced, and, instead of going to the limit of the field, or other temporary barrier, the pillars are taken out as the workings in the solid progress, keeping a range of two or three pillars between, as may be found necessary. The principal advantages derived from this change are, the coal is worked out more expeditiously, the openings are reduced, and the exposure of the broken coal is of shorter continuance.

Fig. 9 shows the Lancashire method of coal working; Lancashire and, to convey a general idea of the practical arrangements, the progress of the excavations are shown at different periods. (See sketch.) The width of the openings (or drifts) formed in the solid vary according to the nature of the roof, &c.; where favourably situated, they range from five to six yards in width. By this method the whole of the coal is intended to be worked away; and the order in which the pillars are taken out is shown.

Several attempts have been made to introduce self-acting machines to assist the miner in extracting the coal from its cutting and native bed. Hitherto these have failed, or from other causes excavating fallen into disuse. The late extraordinary demand for workmen, particularly in Lancashire, has induced the very intelligent engineer for the Earl of Balcarres, Mr William Peace, to invent a machine for performing the laborious operation of "holing" or undermining the coal. It is peculiarly adapted for longwall working, or any method by which the coal is worked in extensive ranges. The holing or undermining averages from four to six inches deep, and extends upwards of a yard under. This operation may be performed in the pavement, or parting, as freely as in the coal; and by this change it is not too much to anticipate from eight to nine-tenths of the coal in a round or marketable state.

Plate CLXXXI, figs. 1, 2, and 3, will illustrate the machine, and convey an idea of the manner in which it works. Referring to it, AAA the frame, upon which is fixed one or more cylinders BB, arranged so as to turn a crank shaft CC, fixed to the frame, as is also another shaft DD. This latter is capable of being turned by the former by means of metre or bevel wheels EEE; upon the lower end of the

Colliery. latter shaft (DD) is placed a wheel termed the driving wheel, having upon its periphery a groove with suitable projections for working into and propelling a chain or band.

Beneath, or to the side, or both, of the frame, is fixed temporarily or otherwise a lever, the extremity of which is constructed to carry a wheel called the terminal wheel, marked

Note.—The different shades show the progress of the workings at different periods.

Scale 150 yards = an inch.

Fig. 9.

HH; a chain or band is made to pass round the driving and terminal wheels, and by means of the driving wheel (FF) it is made to revolve. Into the chain are fixed cutters of different forms (see the parts marked 4, 5, 6, and 7), which, when the machine is in action, revolve with it, and upon being pressed or drawn against the coal, erode and excavate the same. The distance of the excavation from the face of the coal is governed by the dimensions of the machine, and by the length of the lever, and the distance between the driving and terminal wheels. The arrangements of the lever allow it to revolve, and to excavate any given range; see dotted lines fig. 1.

If found necessary, two or even three levers may be in operation at the same time, and arranged to cut in any direction. Other parts of the machine not particularly described are capable of elevating and depressing the front part of the machine, marked V, T, U, W; and those marked X, Y, Z, and K are capable of propelling the machine whilst at work, by acting against the prop.

The power employed to drive the machine (in the opinion of the inventor) may be steam, water, gas, or atmospheric air under pressure; and, in the latter case, the air may be used after having worked the machine for ventilating, or improving the ventilation of the mines.

The success of this invention is of considerable importance to the mining interest, and may ultimately prove a source of profit, as well as a convenience, to many extensive mining concerns.

The colliery tenant in carrying on his mining operations

under the pillar system, has frequently to contend with difficulties arising from the peculiar nature of the roof or pavement of the coal. The most formidable of these are creeps and sits. A coal seam with a soft pavement and a hard roof is the most subject to a creep. The first creep indication is a dull hollow sound when treading on the pavement or floor, probably occasioned by some of the individual layers parting from each other as shown at a, fig. 10;

Fig. 10.

the succeeding stages of creep are shown at b, c, d, f, and g, in the same figure; the latter being the final stage, when the coal begins to sustain the pressure from the overlying strata, in common with the hoved pavement.

Sits are the reverse of creeps; in the one case the sits pavement is forced up, and in the other the roof is forced or falls down, for want of proper support or tenacity in itself.

This accident generally arises from an improper size of pillars: some roofs, however, are so difficult to support that sits take place where the half of the coal is left in pillars.

Colliery. Fig. 11 will convey a general idea of the appearance of sites, k, m, n, showing different stages.

It is proper to remark that these obstacles are easily overcome under the longwall method of coal-working.

Ventilation forms an indispensable prerequisite to mining. Its importance is becoming more generally understood, and of late years it has been the subject of much ingenious discussion; and when we consider that the efforts of the scientific and inventive have until lately been baffled in carrying out a salubrious ventilation by artificial means in the houses of parliament, the uninitiated in coal mining will readily conceive the greater difficulties the miner has to contend with in maintaining a healthy atmosphere, sometimes 1800 feet below the surface of the earth; where, imured in gloom, and surrounded by noxious gases, he has to lead in various forms, and subject to many interruptions, streams of air through the devious courses and windings of the mine, and often extending over many hundred acres. These gases (above alluded to), carbonic acid and carburetted hydrogen, may be termed the natural products of the mine; to expel them is impossible, to control their destructive effects is all that the most sanguine can anticipate; and the remedial means hitherto used has been forcing ample currents of atmospheric air through the farthest recesses of the mine. In principle, this does not admit of much variety; two separate communications with the surface being required, the one to act as an inlet to the mines, and the other as an outlet from them, in mining termed downcast and upcast shafts.

If the shafts A B, fig. 12, were of equal depth from the horizontal plane, and connected by the mine C, the air would fill the openings and remain quiescent. If the one were to the dip of the other, but communicating with the surface at a higher level, as by fig. 13, it would sometimes happen in summer, that D would be the downcast, and E the upcast; and in winter, E the downcast, and D the upcast. These conditions are induced by the temperature of the earth at a certain

depth being nearly constant, while the atmosphere is changeable; the column of air in D d being at a lower temperature in summer than the column of air E e, and the reverse in winter.

To overcome these natural difficulties, and produce a

continuous movement or current, artificial means are resorted to, and the air in the upcast is dilated, by being passed over or brought in close contact with a fire or furnace; see Plate CLXXIX., fig. 3, where the air passes over the furnace B into the upcast shaft A. This method of producing artificial ventilation seems to have been described by Rodolphus Agricola in the sixteenth century. In his book De re Metallica he speaks of the method of drawing the foul air out of a mine by suspending a large fire in the middle of the shaft—a method which has been practised in mines ever since his time.

There have been various schemes for inducing a current of air below ground. Our space here will not allow us to enter into a description of them; but generally speaking, they have all given place to the furnace, which for simplicity and economy stands unrivalled. The only feasible objection yet offered against its universal use, is the probability that the return air in fiery collieries, after having traversed extensive wastes, might produce explosion when brought in contact with the flame of the furnace. In collieries so situated, a proper precaution is adopted for preventing explosions, and the return air is led into the upcast shaft by what is termed a dumb drift, as at C, Plate CLXXIX., fig. 3. Sometimes a chimney is situated near to the upcast shaft (on the surface), into which the return air can be taken, and when of sufficient capacity, it materially assists in ventilation. Plate CLXXIX., fig. 4, is an illustration of it, D the furnace, E the shaft, and S the chimney.

The size of the furnace is proportioned to the requirements of the mine, and its power is the increase of temperature it imparts to the column of air in the shaft in which it is situated.

"It is a law of expansion for atmospheric air and all gases, that they dilate almost equally and very nearly in proportion to the increase of temperature. According to Magnus and Regnault, 1000 cubic inches of air at the freezing temperature increase in bulk to 13,665 cubic inches at the temperature of boiling water, or 212°. This law of expansion applies equally to air in a state of motion as to air in a state of rest; and if we wish to know the force of the draught occasioned by an increase of temperature, according to Montgolfier, ascertain the difference in height between two equal columns of air, when one is heated to a certain temperature, the other being the temperature of the external air, and the force of the draught, or the rate of efflux is equal to the velocity that a heavy body would acquire by falling freely through this difference of height.

"Now the space through which a heavy body falls in perpendicular height in one second is rather more than sixteen feet; but by the law of accelerating forces, the velocity of a falling body at the end of any given time is such as would carry it in an equal time through twice the space through which it has fallen in that time; or the velocity in feet per second is equal to eight times the square root of the number of feet in the fall.

"When the force of the draught of a chimney is the difference in weight between two columns of air caused by the expansion of one of these columns by heat, the decimal .002036, which represents the expansion of air by 1° of Fahrenheit, must be multiplied by the number of degrees the temperature is raised, and this product again by the height of the heated column. Thus, if the height of the column is 50 feet, and the increase of temperature 20°, we have $20\; \backslash times\; .002036\; \backslash times\; 50\; =\; 2.036$ feet; 52.036 feet of hot air will balance 50 feet of the cold air; and the velocity of efflux of the heated column when pressed by the greater weight of the colder column, will be equal to $8\backslash sqrt\{2.036\}\; =\; 11.36$ feet per second.

"By the same means, the efflux of air under any given pressure can also be calculated. The pressure being known, we calculate the height of a column of air equal in weight

to this pressure. Thus if the pressure be equal to one inch of mercury, water is 827 times the weight of air, and mercury 13.5 times the weight of water; therefore $827\; \backslash times\; 13.5\; =\; 11,164$ inches or 930.4 feet, and according to the rule $8\backslash sqrt\{930.4\}\; =\; 244$ feet per second for the velocity of efflux under the pressure of one inch of mercury.

“Allowance must be made for loss by friction, which will vary according to the nature and size of the opening, and also according to the velocity of the air.”

“The retardation of the air by friction in passing through straight tubes (or air courses) will be directly as the length of the tube, and the square of the velocity, and inversely as the diameter.”¹

If the courses are of equal length but of different area, the quantities of air passed along them will not be in proportion to the area, but as the square root of the diameter of the opening multiplied by the sectional area or nearly. When the courses (for air in a mine) vary in length, the supply is governed by regulators, so that the short courses (which under similar circumstances with the long ones would pass greater quantities of air) have their areas contracted, consequently the velocity of the air increased; and as the resistance of air is as the length of the course and the square of the velocity, a uniform resistance is thus produced, and a proper distribution of air throughout the various openings maintained.

A current of air being induced, it is then taken in the most direct manner (avoiding a tortuous course) to the working parts, by what are termed air-courses or air-ways. These when formed require to be made substantial, adequate to any future emergency, and proportioned to the currents desirable in the different courses and openings of the mine. The air in the working parts of a mine cannot be properly conducted with due attention to the comfort of the workmen at a higher velocity than 3 or 3½ feet per second. In the main intake courses it may be increased to 4 or 5 feet per second; but as a high rate of velocity entails a considerable loss by friction, the air, instead of being taken in one undivided column, is led off (“split”) near to the downcast by branches into the working parts, and from that into the main return, where the velocity may range from 8 to 20 feet per second.

The most intelligent and best informed in such matters aim at large air-courses, and a low rate of velocity in the interior of the mine, compared with that in the upcast; and though it was until lately advocated in theory, that the upcast should be of greater dimensions than the downcast, viz., equal to the expansion of the air, practical men had generally acted contrarily, on the well authenticated fact, in practice, that an upcast of less dimensions than the downcast was the more certain and constant in its action. The advantage gained by a comparative small upcast, is the high rate of velocity the air requires to travel in it, and which completely baffles the effects of surface currents so often detrimental to ventilation by large upcasts, and where counter-currents are frequently produced. Though there is no practical limit to splitting or dividing air, it is evident that it can only be profitably carried out when in certain proportion to the outlet, or upcast; and though the proportion has not been satisfactorily defined by experience, it has been acted upon in the following ratio: that when the sectional area of the air-courses is as three or four to one (the upcast), the effect will be a superior ventilation, other conditions being properly arranged.

It has also been laid down as a practical rule for regulating the ventilation of collieries, that under ordinary circumstances a certain amount of air should be provided for each workman; say from 100 to 200 cubic feet per minute; and in fiery collieries, from 400 to 600 cubic feet per minute; but no

general rule can be perfectly applicable to the ever changing conditions of a colliery, and where “wastes” of dissimilar extent, and systems of working entirely opposite exist.

Under the system of working coal by longwall, Plate CLXXV., fig. 1, where the openings never exceed a seventh of the excavations (sometimes not a fourteenth), the ventilation is simple and effective:—the air is divided at the bottom of the downcast, circulates in the direction of the arrows along the dip-head levels AA, round the faces into the mine leading to the ventilating furnace; over it, and into the upcast shaft, assuming nearly a direct course, and sweeping in its progress the gases liberated spontaneously and by combustion, and other noxious vapours of the mine.

The system of ventilation by pillar working is more intricate. There are various obstacles to contend with: the most insuperable of these are, the discharge of carburetted hydrogen gas, induced by the great section of coal exposed; the amount of openings requiring ventilation; the immense friction caused by the tortuous course of the air; and the defectiveness of stoppings, particularly in cases of explosion. Plate CLXXVIII. shows the most modern arrangements for carrying out a safe and wholesome ventilation by this mode of working. Referring to it, the air is “split” near the bottom of the downcast shaft, from which its onward course is indicated by the arrows into the various districts, and returned over the ventilating furnaces into the upcast shaft. The course for the air current is, in general, guided by doors and stoppings; which also act as regulators for the proper distribution of the air into the various working parts of the mine. Stoppings are sometimes composed of brick and lime, sometimes of wood, and not unfrequently of loose stones taken from the mine. Trap doors are moveable stoppings made of wood placed in roadways, along which the products of the mine require to be taken.

Sir Humphry Davy’s invention (viz. the safety lamp), in connection with the ventilation of mines, is too well known to require description. For the principle upon which it is constructed, see the articles DAVY and SAFETY LAMP. When first introduced, it was used to test the state of the mines previous to the workmen going to their work; and this seems to have been the original intention of the inventor. However, its use in certain mining districts has been considerably extended, and some of the most extensive collieries in the world are now lighted wholly by it. Regarding the propriety of this, practical men are not agreed. Certainly, to those unaccustomed to the daily use of the safety lamp, it seems rather a fragile article, upon which hundreds of lives should be constantly dependent.

Under the most rigorous management, and improved system of ventilation, partial explosions from various causes frequently happen. These are seldom heard of beyond the immediate districts in which they occur; it is only when some dreadful havoc has been made, by a sweeping explosion, that the public hear of those appalling scenes of death and misery which result therefrom.

A very correct description of such is to be found in Ure’s Dictionary, at p. 990, from which the following is extracted:—

“The catastrophe of an explosion in an extensive coal-mine is horrible in the extreme. Let us imagine a mine upwards of 100 fathoms deep, with the workings extended to a great distance under the surrounding country, with machinery complete in all its parts, the mining operations under regular discipline, and railways conducted through all its ramifications, the stoppings, passing doors, brattices, and the entire economy of the mine, so arranged, that every thing moves like a well regulated machine.

“A mine of this magnitude at full work is a scene of cheering animation and happy industry; the sound of the

¹ Warming and Ventilation, by C. Tomlinson.

Colliery. hammer resounds in every quarter, and the numerous carriages, loaded or empty, passing swiftly to and fro from the wall-faces to the pit-bottom, enliven the gloomiest recesses. At each door a little boy, called a trapper, is stationed, to open and shut it. Every person is at his post, displaying an alacrity and happiness pleasingly contrasted with the surrounding gloom. While things are in this merry train, it has but too frequently happened, that from some unforeseen cause, the ventilation has partially stagnated, allowing a quantity of the fire-damp to accumulate in one space to the explosive pitch; or a blower has suddenly sprung forth, and the unsuspecting miner entering this fatal region with his candle, sets the whole in a blaze of burning air, which immediately suffocates and scorches to death every living creature within its sphere; while multitudes beyond the reach of the flame are dashed to pieces by the force of the explosion rolling like thunder along the winding galleries.

"Sometimes the explosive flame seems to linger in one district for a few moments, then, gathering strength for a giant effort, it rushes forth from its cell with the violence of a hurricane, and the speed of lightning, destroying every obstacle in its way to the upcast shaft. Its power seems to be irresistible. The stoppings are burst through, the doors are shattered into a thousand pieces; while the unfortunate miners, men and boys, are swept along with an inconceivable velocity in one body, with the horses, carriages, corves, and coals. Should a massive pillar obstruct the direct course of the aerial torrent, all these objects are dashed against it, and there prostrated, or heaped up in a mass of common ruin, mutilation, and death. Others are carried directly to the shaft, and are either buried there amid the wreck, or are blown up and ejected from the pit-mouth. Even at this distance from the explosive den, the blast is often so powerful that it frequently tears the brattice walls of the shaft to pieces, and blows the corves suspended in the shaft as high up into the open air as the ropes will permit. Not unfrequently, indeed, the ponderous pulley-wheels are blown from the pithead-frame, and carried to a considerable distance in the bosom of a thick cloud of coals and coal-dust brought up from the mine by the fire-damp, whose explosion shakes absolutely the superincumbent solid earth itself with a mimic earthquake. The dust of the ruins is sometimes thrown to such a height above the pit as to obscure the light of the sun. The silence which succeeds to this awful turmoil is no less formidable; for the atmospheric back-draught rushing down the shaft denotes the consumption of vital air in the mine, and the production of the deleterious choke-damp and azote.

"Though many of the miners may have escaped by their distance in the workings from the destructive blast and the fire, yet their fate may be more deplorable. They hear the explosion, and are well aware of its certain consequences. Every one anxious to secure his personal safety strains every faculty to reach the pit-bottom. As the lights are usually extinguished by the explosion, they have to grope their way in utter darkness. Some have made most miraculous escapes, after clambering over the rubbish of fallen roofs, under which their companions are entombed; but others wandering into uncertain alleys, tremble lest they should encounter the pestilential airs; at last they feel their power, and aware that their fate is sealed, they cease to struggle with their inevitable doom, they deliberately assume the posture of repose, and fall asleep in death."

Hitherto no human foresight has been able to prevent the recurrence of these dreadful calamities. Much has been done to prevent them, and much remains still to do. But though the prevention of explosions goes to the root of the evil, the far more fertile source of death is from the effects of the after-damp. It is, therefore, of sufficient importance for those interested in mining to devise means for the mitigation of the evil, or contrive that an arrangement of work-

ing be carried out, so that when explosions do happen, the effects of the after-damp (by which 75 per cent. are killed) may be rendered less fatal.

The writer of this has long felt the hopelessness of the miner's case in the event of an extensive explosion, whereby the arrangements for ventilation are entirely subverted (even though they escape the fire and the blast); and he submits a plan showing an arrangement of working and ventilation, by which he feels assured, that in case of an explosion, few, if any, will lose their lives from the effects of the after-damp. He does so with deference to that intelligent body whom it concerns as proprietors and managers of mines, and with a wish that it may prove beneficial to the miners, a most useful and hardy class of men, fearless from being all their lifetime inured to dangers; but from their habits, generally they and their families are ill-prepared to encounter those adversities of life, resulting from the accidents to which their employment constantly exposes them.

Plate CLXXX, fig. 1, will illustrate this arrangement of working and ventilation. Referring to it, the coal is worked on the longwall system, and divided into suitable districts, 1, 2, 3, 4. The ventilation is maintained by two pits, upcast and downcast.

The course of the air is indicated by the arrows; it is split at the bottom of the downcast, and taken into the several districts as may be required.

The advantages anticipated from this arrangement of working, in the event of an explosion, are—the air courses will be preserved; the districts will remain perfectly isolated; and from the peculiar situation of the upcast, the ventilating currents must of necessity make the circuit of the mine before they can get into it.

When workings are made a dipping of the pit-bottom, Dip work-engines are often used underground for drawing the coalings, and water to the dip-head level. This is an irregular and objectionable mode of working, and where sinkings are readily made from the surface, it is generally found more economical to do so.

However, there are situations where limited portions lie to the dip of going works, which could not be taken out to advantage by any other arrangement.

It frequently happens that colliery operations are interrupted by dislocations, but seldom to such an extent as to cause new workings to be made from the surface. The general mode of overcoming such difficulties, and continuing the workings of the colliery, is to form connections by stone drifts, or mines; and where practicable these are found the most convenient. Blind pits are sometimes used for the same purpose; and in deep pits, where two or more seams lie within a short distance of each other, they are frequently connected in this way, and the whole of the coals lowered to the lowest seam by a drop. The term blind pit is used in contradistinction to one sunk from the surface. Referring to Plate CLXXXIX, fig. 1, where a drop is shown, k is the blind pit, made of such dimensions as to allow the cages ff to ascend and descend; c a wheel, the diameter of which is exactly the distance between the centres of the two cages less the thickness of the rope,—it is placed at the top of the pit, high enough to allow the bottom of the cage to rest level with the seam of coal aa; a flat rope g, attached to the cages, works on the wheel; a break m is applied to the underside of it, clear of the rope, and connected with the levers nn, which regulates the descent. The friction or grip of the rope on the wheel is sufficient to prevent its slipping when a full hutch is on the cage. In order to preserve the equilibrium, a rope is attached to the bottom of each cage g', and passes round the pulley e', placed below the bottom of the seam bb.

After the coal is taken down, it is put into boxes, baskets, Drawing or hatches, fitted with wheels for running upon rails, and hauling is thus conveyed by manual labour or otherwise to the pit-

Colliery. bottom. When the seams lie steep, slope roads and self-acting inclines are made to lessen the labour of drawing; and where the roads are long, horses are used for the same purpose with advantage.

Pit-bottom arrangements. Having brought the coals to the bottom of the shaft, and placed them upon the cage, it is necessary to signal to the engineman at the surface to wind them up; which is performed by means of a wire led down the shaft attached to a hammer at the surface. The order in which the signals are given vary in detail at different collieries, according to the nature of the under-ground arrangements; in general, however, when the hammer gives one stroke, the engineman knows that coals are to be drawn up; when three, that men are to be drawn up, and so on.

Above-ground arrangements. The improvements in winding machinery, and general arrangements above ground, have advanced considerably within the last twenty years. The present system of winding with cages, guided in the shaft by wooden conductors, is almost universally adopted throughout the leading mining districts of the kingdom.

The conductors (commonly made of wood 3½ inches square) reach from the pit-bottom to the pit-head pulley, and are stayed at proper intervals. Cages are simply platforms attached to the ropes for carrying the loaded hutches, and are furnished with guides for the conductors to work in; which renders the ascent safe and steady. The form of cages vary; sometimes they are made to hold one hutch and sometimes two, either alongside or one above the other; but when windings are deep, and a large output required, three or four hutches are taken up at once. The arrangement of conductors and cages has led to the introduction of safety apparatus for disengaging the cage in case of overwinding or stopping its descent, in the event of the rope breaking. The following figures (14, 15, 16) show a very ingenious and effective apparatus of this description, invented and patented by Messrs White and Grant, engineers, Glasgow.

On referring to the figures 14, 15, and 16, the mode of action will be readily understood; fig. 15 shows the manner in which the pinions operate upon the conductors when the rope breaks, or when disengaged by the catch h; aa the wooden conductors; BB eccentric toothed pinions, connected with spiral springs dd; C the slide bar from which the cage is suspended, and to which are attached the springs ff; and h the catch, which disengages the rope in case of overwinding, or when it is brought in contact with the pit-head frame k. The use of the springs ff is to ensure the action of the pinions BB; they also prevent a sudden strain being put upon the rope when the load is lifted—an important precaution when wire-ropes are used.

In glancing at the history and improvements in mining machinery, the genius and far-sightedness of the late Mr John Curr stands out prominently. He was the inventor of cast-iron hutch-rails; and his designs, upwards of half a century ago, have not, up to this time, been improved upon. In 1798, he patented a system of winding with guides and conductors, differing very little in principle from that in use at present; by his design the hutch was suspended from a cross bar, guided by con-

ductors; and at the present day it might be a question worth the consideration of owners of deep collieries, where heavy cages are in use, whether Curr's plan, or a modification of it, would not economize the present system of winding machinery. He also invented the flat hemp rope, which is unrivalled for the purpose to which it is applied. Thus, the truly inventive genius of Curr may be recognised in the improvements of the present day, as in all probability White and Grant's ap-

paratus would never have existed had not the previous design of Curr (viz., the conductors) laid the ground-work of it.

Plate CLXXXII. shows the general arrangements for winding, screening, and carrying away. Referring to it—a a the drums on which the ropes wind, b the pit-head pulleys—it will be observed the drums are on different shafts, the advantage of which is that the ropes bend always one way. Practice has proved that when both drums are on the same shaft, the one that overwinds lasts longest; and it is now considered economical, and in many cases convenient to use two shafts instead of one: c the engine-house, &c., d d the boilers, e e the engine and pit-head framing, h the cage, n n conductors, l l folding boards, placed so that the cage opens them in being brought up the pit, when they again shut for it to rest upon; this enables the banksman to draw the loaded hutch from the cage on to the platform f, and replace it by an empty one; they are again opened to allow the cage to pass through (by the engineman) by means of the rods m m; t the tumbler for emptying the hutches into the screen g, so constructed, that when the loaded hutch is run into it, the extra weight past the point of suspension produces the position of the hutch shown by dotted lines. A break or friction wheel controls this movement; and when the hutch is emptied, and the friction removed, the machine falls back into its first position; when the empty hutch is drawn out to make way for the next full one, to be disposed of in a similar way, and so on; h i, the waggons into which the coals and dross fall; k the dross, and i the coal waggon.

To exhibit clearly the relative annual production and value of the coal, anthracite and lignite or brown coal, in the six great coal-producing countries in our globe in the year 1845, the following illustrative statement has been prepared. It is hardly necessary to observe that, in the two preceding years a regular increase has been simultaneously going on in all the countries enumerated, and apparently about a corresponding ratio. The official estimated value of the coal at the places of production is given in the subjoined table:—

The subjoined diagrams represent the relative amounts

Colliery of production of mineral combustibles in these states, likewise in the year 1845:—

From this diagram we find, that Great Britain (although considerably underrated) produces seven times more than the United States of America, from six to seven times more than Belgium; from seven to eight times more than France, and nine times more than Prussia.

According to recent estimates, the annual produce of coal in Great Britain considerably exceeds 40,000,000 tons. At the present rate of consumption, the coal deposits of Great Britain will still last more than 1500 years; and by an improved method of working, viz., "longwall," this time might be extended at least 400 years. It may require some time to introduce this mode of working for economizing coal-fields; but it is nevertheless a point deserving of careful consideration (seeing that our most valuable and easily obtained seams are at present being rapidly exhausted), and sufficiently important to enlist the interest of a great manufacturing country, whose commercial success is in a great measure dependent upon her collieries or coal mines.

COAL is plentifully distributed throughout that division

of the earth's crust termed by geologists the coal measures. It is readily recognised from the strata in which it is found. It has a blackish appearance, is of less specific gravity (than the other strata), and is very inflammable when brought in contact with heat and flame.

If we omit the earthy impurities, which, when burnt, are known as ashes, and which vary from 0.2 to upwards of 40 per cent. "coal is essentially composed of carbon, oxygen, hydrogen, and nitrogen; and the quality of the coal depends upon the relative proportion of these ingredients."¹

This important mineral is extensively used in navigation; it is the indispensable aliment of industry; and in cold or temperate climates is essential to the health and comfort of the inhabitants.

The following diagrams will convey an approximate idea of the respective areas of coal formation in the principal coal-producing countries of Europe and America. (See Taylor's Statistics of Coal.)

COLLIMATION, LINE or, the line of sight in astronomical and geodetical instruments, as mural circles, transit instruments, sextants, quadrants, theodolites, &c. Thus, in a telescope, the line of collimation is the straight line passing through the centre of the object-glass, at the point where the fine wires or spider-webs intersect each other in its focus. The term is derived from the Latin collimo, to aim at.

COLLIMATION, Error of, the deviation of the actual line of sight, in a telescope, from the centre of the object glass, where it ought to be perpendicular to the horizontal axis. The amount of this deviation must be precisely ascertained and corrected, or allowed for, in order to insure accuracy in the result of the observations.

Among other contrivances for this purpose, the collimator of Captain Kater is used for determining the error of collimation in any principal instrument, by which the necessity of the reversal of the instrument itself is obviated.

COLLINGWOOD, CUTTINER, first Lord Collingwood, a celebrated naval commander, was born at Newcastle-upon-Tyne, on the 26th of September 1750. He was early sent

to school; and when only eleven years of age he was put on board the Shannon, then under the command of Captain (afterwards Admiral) Brathwaite, a relation of his own, to whose care and attention he was in a great measure indebted for that nautical knowledge which shone forth so conspicuously in his subsequent career. After serving under Captain Brathwaite for some years, and also under Admiral Roddam, he went in 1774 to Boston with Admiral Graves, who in the year following presented him with a lieutenancy. After occupying the same rank in two other vessels, he was in 1779 made commander of the Badger; and shortly afterwards, post-captain of the Hinchinbroke, a small frigate. In the spring of 1780 that vessel, under the command of Nelson, was employed upon an expedition to the Spanish Main, where it was proposed to pass into the Pacific by a navigation of boats along the river San Juan and the lakes Nicaragua and Leon. The attempt failed, and most of those engaged in it became victims to the deadly influence of the climate. Nelson was promoted to a larger vessel, and Collingwood succeeded him in the command. It is a fact worthy of record, that the circumstance

¹ Government Report by Sir H. de la Beche, and Dr Lyon Playfair, in 1846.

of the latter succeeding the former should so very frequently have occurred from the time when they first became acquainted, until the fatal day when the star of Nelson "dropp'd from its zenith," and set at Trafalgar—giving place to that of Collingwood, less brilliant certainly, but not less steady in its lustre.

After commanding in another small frigate, Collingwood was promoted to the Sampson, of sixty-four guns; and in 1783 he was appointed to the Mediator, destined for the West Indies, where with Nelson, who had a command on that station, he remained until the latter end of 1786. With Nelson he warmly co-operated in carrying into execution the provisions of the navigation laws, which had been infringed by the United States, whose ships, notwithstanding the separation of the countries, continued to trade to the West Indies, although that privilege was by law exclusively confined to British vessels. In 1786 Collingwood returned to England, where, with the exception of a voyage to the West Indies, he remained until 1793, in which year he was appointed captain of the Prince, the flag-ship of Rear-admiral Bowyer. About two years previous to this event he had entered into the matrimonial state. This alliance was a fortunate one, and continued to be a solace to him amidst all those privations to which the life of a seaman must ever be subject.

As captain of the Barfleur, Collingwood was present at the celebrated naval engagement which was fought on the 1st of June 1794; and on that occasion he displayed equal judgment and courage. On board the Excellent he shared in the victory of the 14th of February 1797, when Sir John Jarvis humbled the Spanish fleet off Cape St Vincent. His conduct in this engagement was the theme of universal admiration throughout the fleet, and greatly advanced his fame as a naval officer. After blockading Cadiz for some time, he returned for a few weeks to Portsmouth to repair. In the beginning of 1799 Collingwood was raised to the rank of vice-admiral, and hoisting his flag in the Triumph, he joined the Channel fleet, with which he proceeded to the Mediterranean, where the principal naval forces of France and Spain were assembled. Collingwood continued actively employed in watching the enemy, until the peace of Amiens restored him once more to the bosom of his family.

The domestic repose, however, which he so highly relished, was cut short by the recommencement of hostilities with France; and in the spring of 1803 he quitted the home to which he was never again to return. The duty upon which he was employed was that of watching the French fleet off Brest; and in the discharge of it he displayed the most unwearied vigilance. Nearly two years were spent in this employment: but Napoleon having at length matured his plans and equipped his armament, service of a more active description was immediately to be expected. The grand struggle, which the nations looked forward to with breathless suspense, and which was to decide the fate of Europe and the dominion of the sea, was close at hand. The enemy's fleet having sailed from Toulon, Admiral Collingwood was appointed to the command of a squadron, with orders to pursue the enemy. The combined fleets of France and Spain, after spreading terror throughout the West Indies, returned to Cadiz. On their way thither they bore down upon Admiral Collingwood, who had only three vessels with him: but he succeeded in eluding the pursuit, although chased by sixteen ships of the line. Ere one half of the enemy had entered the harbour he drew up before it and resumed the blockade, at the same time employing an ingenious artifice to conceal the inferiority of his force. But the combined fleet was at last compelled to quit Cadiz; and the battle of Trafalgar immediately followed. The brilliant conduct of Admiral Collingwood upon this occasion has been much and justly applauded. It is unnecessary here to enter into a full detail of the battle (for an ac-

count of which see the article BRITAIN); but a short outline is necessary, in order to show that no small portion of the glory of that day belongs to Collingwood. The French admiral drew up his fleet in the form of a crescent, and in a double line, every alternate ship being about a cable's length to windward of her second, both ahead and astern. The British fleet bore down upon this formidable and skillfully arranged armament in two separate lines, the one led by Nelson in the Victory, and the other by Collingwood in the Royal Sovereign. The latter vessel was the swiftest sailer, and having shot considerably ahead of the rest of the fleet, was the first engaged. "See," said Nelson, pointing to the Royal Sovereign, as she penetrated the centre of the enemy's line, "see how that noble fellow Collingwood carries his ship into action!" Probably it was at the same instant that Collingwood, his mind kindled up with the same generous and ennobling sentiments, and as if in response to the observation of his great commander, remarked to his captain, "What would Nelson give to be here!" The consummate valour and skill evinced by Collingwood had a powerful moral influence upon both fleets. It inspired with unbounded confidence in their commanders those who scarcely needed any incentive to do their duty in the bravest manner: and, on the other hand, the French admiral, struck with the noble daring displayed, was seized with a dark presentiment of the fate which a few short hours too fatally realized. It was with the Spanish admiral's ship that the Royal Sovereign closed; and with such rapidity and precision did she pour in her broadsides upon the Santa Anna, that the latter was on the eve of striking in the midst of thirty-three sail of the line, and almost before another British ship had fired a gun. Several other vessels, however, seeing the imminent peril of the Spanish flag-ship, came to her assistance, and hemmed in the Royal Sovereign on all sides; but the latter, after suffering severely, was relieved by the arrival of the rest of the British squadron; and not long afterwards the Santa Anna struck her colours. The result of the battle of Trafalgar, and the expense at which it was purchased, are well known. On the death of Nelson, Collingwood assumed the supreme command; and by his skill and judgment greatly contributed to the preservation of the British ships, as well as of those which were captured from the enemy. He was raised to the peerage, and received the thanks of both houses of parliament, with the grant of a pension of £2000 per annum.

From this period until the death of Lord Collingwood no great naval action was fought; but he was much occupied in important political transactions, in which he displayed uncommon tact and judgment. Being appointed to the command of the Mediterranean fleet, he continued to cruise about, keeping a watchful eye upon the movements of the enemy. But his health, which had begun to decline previously to the action of Trafalgar in 1805, seemed entirely to give way; and he repeatedly requested government to be relieved of his command, that he might return home; but he was urgently requested to remain, on the ground that his country could not dispense with his services. This conduct has been regarded as harsh, and certainly it does not appear very amiable when we consider the age of Lord Collingwood, his long and active services, and the arduous nature of the enterprise in which he had embarked. But it cannot be denied that the remarkable good sense and political sagacity which he displayed in the various transactions with which he was connected at that critical and eventful period, in some measure affords a palliation of the conduct of the government which decreed that he should perish at his post. And it puts the estimation in which he was held in a very conspicuous point of view, that amongst the many able admirals, equal in rank and duration of service, none stood so prominently forward as to command the