Jeremy, a learned English nonjuring divine, born at Stow Qui, Cambridgeshire, in 1650, and educated at Caius College, Cambridge. His first appointment was to the small rectory of Ampton, near St Edmund's Bury, Suffolk, which, after six years, he resigned in order to proceed to London, where in 1685 he was made lecturer of Gray's Inn. But the change of government at the revolution soon rendered the public exercise of his function impracticable. He was committed to Newgate for writing in favour of the dethroned monarch; and again on a charge of carrying on a treasonable correspondence with the enemies of the movement; but he was released on both occasions without trial, by the intervention of his friends. So far did he carry his scruples at this period, that he submitted to confinement rather than make a tacit acknowledgment of the jurisdiction of the court by accepting his liberty upon bail. In the two following years he continued to harass the government by his publications; but for his boldness in granting absolution to Sir John Friend and Sir William Perkins at their execution, he was obliged to flee, and for the rest of his life continued under sentence of outlawry. From that time forward he employed his leisure in literary works, which were less political in their tone. In 1698 he published a short treatise in the style of Pryme's famous Histrio-mastix, entitled a Short View of the Immorality and Profaneness of the English Stage, which engaged him in a lengthened controversy with Congreve, Vanbrugh, and the other wits of the day. The book abounds in hypercriticism and in useless display of learning, neither intrinsically valuable nor conducive to the argument. Yet, in the words of Mr Macaulay, "when all deductions have been made, great merit must be allowed to the work. There is hardly any book of that time from which it would be possible to select specimens of writing so excellent and so various. To compare Collier with Pascal would, indeed, be absurd; yet we hardly know where, except in the Provincial Letters, we can find mirth so becomingly and harmoniously blended with solemnity as in the Short View. In truth, all the modes of ridicule, from broad fun to polished and antithetical sarcasm, were at Collier's command. On the other hand, he was complete master of the rhetoric of honest indignation. We scarcely know any volume which contains so many bursts of that peculiar eloquence which comes from the heart and goes to the heart. Indeed, the spirit of the book is truly heroic."

In order fairly to appreciate it, we must remember the situation in which the writer stood. He was under the frown of power. His name was already a mark for the invectives of one-half of the writers of the age, when, in the cause of good sense, good taste, and good morals, he gave battle to the other half. Strong as his political prejudices were, he seems on this occasion to have laid them entirely aside. He has forgotten that he is a Jacobite, and remembers only that he is a citizen and a Christian. Some of his sharpest censures are directed against poetry which had been hailed with delight by the Tory party, and had inflicted a deep wound on the Whigs. It is inspiring to see how gallantly the solitary outlaw advances to attack enemies formidable separately, and, it might have been thought, irresistible when combined; distributes his swashing blows right and left among Wycherley, Congreve, and Vanbrugh; treads the wretched Tom D'Urfey down in the dirt beneath his feet, and strikes with all his strength full at the towering crest of Dryden. The effect produced by the Short View was immense. The nation was on the side of Collier. The general belief was, that Dryden would take the field against him; and all the wits anticipated a sharp contest between two well-paired combatants. But Dryden's conscience smote him; he stood abashed, like the fallen archangel at the rebuke of Zephon. At a later period he mentioned the Short View in the preface to his Fables. He complained with some asperity of the harshness with which he had been treated, and urged some matters in mitigation; but, on the whole, he frankly acknowledged that he had been justly reproved.

Collier afterwards executed a translation of Moreri's Historical and Geographical Dictionary, which appeared in 4 vols. fol., 1701, 1705, 1721. After this he published An Ecclesiastical History of Great Britain, chiefly of England, in 2 vols. fol., 1708 and 1714. His Essays upon several Moral Subjects, in 3 vols. 8vo, published between 1697 and 1709, display considerable learning, ability, and taste. In 1701 he published a translation of Antinmus's Meditations. His last work was a volume of Practical Discourses, published in 1725. Collier died of the stone, April 26, 1726. 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 1649, 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 spoyle the taste of drinck, 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.

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.

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:

**SUPERFICIAL ACCUMULATIONS**

- **TERTIARY** - Sandstone, Marls, and Plastic Clay - Chalk and Lias formation

- **SECONDARY FORMATION** - New Red Sandstone And Magnesian Lime - Coal measures - Mountain Limestone - Old Red Sandstone, Silurian Limestones, and Sandy Slates - Clay Slates, Mica and Talc Schists, Gneiss rocks

- **PRIMARY** - Granite

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 wants, shaken coal, saddle-backs, baulks, pot-bottoms, games, hitches, and dykes.

Nips or wants. 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.

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. 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 towards m, interrupted by hitches—A being an upthrow and B a downthrow.

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 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 outcropping 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 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 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 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 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 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:

| S. Wales | France | Saxony | Pennsylvania | Brazil | |----------|--------|--------|-------------|-------| | Carbon, 88 to 95 p. cent. | 80 to 83 | 81 | 85 to 92 | 94 |

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 description 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 greyish-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 Torbanchill being the most valuable in the former, and the Lesmahagow 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 letting 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 for 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 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 proving 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 interior 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 x 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 x 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 won, 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 underwater 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 tubing, 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 L100,000, 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 CLXXVI. 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-crank 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-cranes 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; d the working barrel fitted with stuffing box e; f 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; s the suction of the top set; d the working barrel; c the plunger glanded on the main rod b at r; h clack and door pieces; p pipes; f the landing box which delivers the water at the surface.

In the plan of lifting pumps, fig. 2, a a the bell-cranes, b b the rods, c c the working barrels, f f 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-cranes 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 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.

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.

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.

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 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.

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 shewing modifications of the former.

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 CLXXVI, fig. 1, represents one of the most ancient methods of coal-working, known in Scotland as "stoop room, &c. 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 pillar 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, method, 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 for 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 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.

HH: a chain or hand is made to pass round the driving and terminal wheels, and by means of the driving wheel (PP) 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 liable 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:

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. 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 uninstituted 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, immersed 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 Metalllica 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 $20 \times 0.002036 \times 50 = 2.036$ 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 $8\sqrt{2.036} = 11.36$ 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 $135$ times the weight of water; therefore $827 \times 135 = 11,164$ inches or $9304$ feet, and according to the rule $8\sqrt{9304} = 244$ 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."

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 $3\frac{1}{2}$ 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 larger 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 coalmine 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 everything 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..." 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 shivered 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 working be carried out, so that when explosions do happen, the Colliery 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 coals 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 winnings 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 Blind pit. 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 CLXXIX., fig. 1, where a drop is shown, k is the blind pit, made of such dimensions as to allow the cages f f 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 a a; 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 n n, 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 b b.

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

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.

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 hatches, 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 hatch and sometimes two, either alongside or one above the other; but when windings are deep, and a large output required, three or four hatches are taken up at once. The arrangement of conductors and cages has led to the introduction of safety apparatuses 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 B B; 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 conductors; 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 apparatus would never have existed had not the previous design of Curr (viz., the conductors) laid the groundwork 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, k 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 hatch 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 hatches into the screen g, so constructed, that when the loaded hatch is run into it, the extra weight past the point of suspension produces the position of the hatch shown by dotted lines. A break or friction wheel controls this movement; and when the hatch is emptied, and the friction removed, the machine falls back into its first position; when the empty hatch 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; h the dross, and i the coal wagon.

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:

| Country | Value (£) | |------------------|----------| | Great Britain | 9,450,000| | Belgium | 1,660,000| | United States | 1,373,963| | France | 1,693,106| | Prussian States | 856,370 | | Austrian States | 165,290 |

The subjoined diagrams represent the relative amounts