Colliery, a term applied to coal-mining establishments, including the mines, buildings, and machinery employed. In their simplest form, as now seen in the Alleghany coal field, where the strata lie nearly horizontal, and generally in the hills or mountains above the level of the streams, or common water level, the collieries employ little or no machinery; but at the deep and extensive mines of the Pennsylvania anthracite fields, and in the older mining districts of Europe, these establishments are of immense proportions,, employing hundreds of hands and a vast capital. Primitively, the process of digging coal and other minerals consisted in simply removing the surface earth, and quarrying the coal on the outcrops of the beds, and this was continued even to a late day. The most notable instance of modern surface coal mining was at the old Summit mines of the Lehigh, where the great Mammoth bed was uncovered to the extent of 30 acres, and produced 2,000,000 tons of coal up to 1847, when it was abandoned. The great bed, which was nearly 70 ft. thick at this place, formed an anticlinal with the axis near the surface where the quarry was opened.

A tree which had grown over this spot and extended its roots into the coal bed below, having been uprooted by the wind, revealed the coal to a hunter, who reported the discovery, and from this grew the famous Lehigh coal mines. . From the quarry method, the next step in advance introduced the art of mining, or under-ground work, and the establishment of collieries. Where the coal beds existed above water level, or near the surface, rude excavations were made into the bed; where they were small, simple galleries were formed in the solid coal from 4 to 12 ft. wide, with arched top and without timber. At the old Butterknowle workings on the southwest outcrops of the Newcastle (English) coal field, these galleries are three yards wide, with square pillars of coal of equal dimensions on each side. These mines are supposed to be 200 years old, and are from 40 to 50 ft. deep. In the Richmond,' Va., coal field, galleries of the same character are found, driven at right angles to each other between square pillars, or at random when in faulty ground. These works are also in shallow pits, as all the coal of that field exists below the water level.

They are apparently more than 100 years old, and are situated at Springfield on the N. E. edge of the Richmond coal field, where trees over 100 years of age were found during the year 1857 growing on the heaps of waste extracted from them. The most noted of these in the Pennsylvania anthracite fields were on the outcrops of the Mammoth, locally known as the Baltimore bed, near Wilkesbarre, and on the B bed, known as Smith's bed, below Plymouth, in the lower end of the Wyoming valley. These excavations were large, corresponding to the size of these great beds, and wide enough to admit horses and wagons to drive in and turn in the rooms or galleries thus formed. - All or most of the coal of England and Belgium exists below water level, and is mined by pits. Until the application of steam for general purposes in 1800, both coal and water were raised from these mines by horse power or by women; and this was continued even up to 1845, when the employment of women in the mines was prohibited by act of parliament. During 1842, 2,400 girls and women were at work in the mines of Scotland alone, mostly employed in conveying the coal to the surface.

In some favored localities near the streams, water power was made use of for pumping; in others, horse wains or gins and sometimes hand windlasses were used to raise both coal and water; but more frequently women were employed as beasts of burden, not only to convey the coal along the low entries, in which they could not stand upright, but also up long lengths of ladders from the bottom of small pits to the surface. The work that was performed by women in these old collieries is almost incredible. Robert Bald, in his "General View of the Coal Trade of Scotland" (1808), says: "We have seen a woman take on a load of 170 pounds of coal and travel with this up the dip of the bed, 150 yards, and then ascend a pit by stairs or ladders 117 ft., no less than 24 times during a day of 10 hours." Formerly the colliers of England were practically serfs, and kept in a state of bondage to the proprietors of the collieries where they were born. They were held to be part of the establishment for carrying on the coal mines, and if the mines were leased the colliers were included in the lease.

In the habeas corpus act it was declared "that this present act was in no way to be extended to colliers and salters." But in 1775 an act of parliament declared that colliers and salters were no longer "transferable with the collieries and salt works;" and upon certain conditions they were to be gradually emancipated, while others were prevented from coming into such a state of servitude. Even after the general introduction of the steam engine at the British mines, for raising coal and hoisting or pumping water (though pumps were seldom used until a much later day), women were employed to convey the coal from the mines to the bottom of the pit, a distance of from 100 to 300 yards, with loads of 100 or 150 pounds in bags on their backs, traversing a total distance of nearly 10 miles a day in going and returning. About this time wheelbarrows were also used, and afterward sleds or "cauves," which were pulled by women or boys; and at a still later day "bogies," pushed or pulled by boys, were introduced. These were provided with narrow tram wheels, which ran in grooved rails of wood.

Boys of very tender age were employed in the British mines up to a late date to work the " steel mills," which gave light by the production of sparks from a circular wheel armed with steel striking against flints; as "trappers" to open and shut the many doors then used to regulate and guide the air currents; to blow the small fans often used to convey air to points beyond the range of the air currents; and to "put" or push the bogies. • But for the last 20 years boys under 12 years of age have been prohibited from working in the British coal mines. In Belgium, however, both women and children are still employed in and about the mines. Wages are so small that it requires the united exertions of fathers, mothers, and children to earn a livelihood. - In England, Belgium, and France, most of the coal lies deep below water level, and can only be reached by expensive pits, which are owned and worked by wealthy proprietors or large companies. In the older mining districts, where the outcrop coal has been long since exhausted, or partially worked by the old methods, in which from half to two thirds of the coal was lost, these pits are constantly growing deeper, and now reach a great depth.

W. W. Smith states that a coal pit exists in the province of Hainaut in Belgium, at the colliery des Viviers at Gilly, near Charleroi, which has been sunk 3,411 ft. We do not know that coal has been mined at that 1, 2, 3, etc, pits; a, coal measures; b, Permian; c, cretaceous, etc.; d, slip dike; e, trap dike; g, trap dike; h, Devonian; i, Silurian: k, Cambrian; m, gneiss; n, granite. depth, however. In many cases these pits penetrate the overlying Permian formation, beneath which most of the carboniferous formations of England and France are concealed, and where the existence of coal was formerly doubted. Indeed, more than two thirds of the English coal measures are supposed to lie beneath the more recent rocks; while over 40,-000 sq. m. of France is covered by the Permian, triassic, cretaceous, and tertiary formations, beneath which coal may exist; or, if it does not exist, it is the exception and not the rule. The geological order of the sedimentary rocks requires the existence of the carboniferous below the Permian; and as far as we know, from their outcrop and from the evidence of the deepest pit yet sunk, this succession does in fact prevail, though there may be localities in which the regular order is interrupted.

This alone would create doubt, and make the most enterprising cautious. Yet, step by step, the miners of England have approached this doubtful ground, and are now 2,000 ft. beneath the Permian rocks, where no one but William Smith, the father of English geology, ever dreamed of looking for coal in his day. And this advance into unknown ground will doubtless be continued until the deep coal beds, reposing 10,000 to 20,000 ft. beneath the sea, will be won and worked. - In the great American bituminous fields mining operations are much more diversified than in the bituminous fields of Europe. In the Alleghany and central coal fields the carboniferous rocks are the latest and highest geological formations; consequently their wide horizons, covering nearly 100,000 sq. m., may be penetrated at any point without hazard. While the coal of the former is generally found in the hills or mountains, and accessible by drifts or tunnels above the natural drainage, that of the latter is generally below the water level, yet may be entirely developed by pits less than 1,000 ft. in depth. Of the 17,000,000 tons of coal mined from the Alleghany field in 1871, less than 1,000,000 tons were mined below the water level, and the remainder from drift or tunnel collieries, and generally from the former.

Drift is a technical term for a tunnel, entry, or gallery driven through the coal horizontally, while the tunnel is a horizontal gallery driven through the rocky strata to reach the coal. The dip or undulations of the strata vary considerably, even in coal fields which have a general dip in one direction, or that may be nearly horizontal. These elevations and depressions thus formed in the coal beds are locally termed saddles, horsebacks, swells, troubles, &o.; where they are frequent they interfere seriously with the drainage. In locating collieries these peculiarities of dip are important questions, which may generally be determined by surface indications, when the coal beds and accompanying strata are above the water level. Yet hundreds of thousands of dollars are frequently expended in building railroads, houses, and other colliery appurtenances, before these preliminary investigations are made, and when it is too late to remedy the great inconveniences entailed. Many instances of this kind might be cited in the Alleghany coal field and elsewhere. One on the Philadelphia and Erie railroad involved $500,000 of useless expenditure.

The drift should always be located at the lowest available point of dip (a, fig. 5); but if the lowest point to which mining operations should extend cannot be reached by drift, started on the outcrop of the bed and continued horizontally in the same, a tunnel may be made use of commencing in the rocky strata above or below the coal bed, in order to reach the bed horizontally, and secure natural drainage. "When this mode is not available, the slope or the shaft method is resorted to. In many parts of the Alleghany coal field and its outlying basins the most productive beds of coal are on or near the tops of mountains, or at a considerable.elevation above the valleys. In these situations locomotive railroads are impracticable, and inclined planes are used; they are operated by gravity, the loaded cars in descending drawing up the empty cars. On the Youghiogeny, Pa., and in the Frostburg, Md., mining districts, this form of colliery establishment is in general use; 1,000 tons of coal per day are sometimes run over a single double-track plane.

The most elevated coal of the Alleghany field is about 2,300 ft. above tide, while the lowest is probably 2,000 ft. below the Ohio river, near the mouth of the Great Kanawha, which is considerably deeper than the lowest coals of the central coal field in Indiana, Illinois, or Kentucky, but much less than the deepest coals of the western coal field in Kansas and Colorado, where the lower coal measures are probably 5,000 ft. beneath the tertiary rocks. In the Pennsylvania anthracite fields, however, we find still greater diversity of mining operations as the necessary results of a contorted or highly plicated form of stratification, in which the undulations of dip are most extreme and irregular. In these anthracite coal basins every known plan of drift, tunnel, slope, and shaft is employed. When the coal beds exist in the hills above the water level, drifts and counter-drifts, or upper levels, are used where the outcrop of the bed is exposed in an available locality; otherwise tunnels are made at the lowest practicable point. In these basins the coal beds usually incline at high angles of dip.

However high the mountain may be on which they crop out, it is rare that they do not dip below the water level or into the basins at the base of the mountain; and still more seldom are the beds found in horizontal strata, except in the synclinals or at the bottom of the basins, where they often occur in horizontal position before curving to the opposite dip. The great basins of the anthracite fields are generally bordered by parallel mountain ranges, against the sides of which the coal beds crop out. These mountains, particularly in the interior of the fields, are cut through by numerous watercourses, which form gaps or gorges at right angles to the strike of the strata, and in these the outcrops of the coal beds descend to the water level. Thus the broken ends of the strata are exposed, and in these most of the drift collieries of the anthracite basins have been located. But when the outcrops are not thus exposed, and the elevation of the outcrop is sufficiently high above water level, the coal beds are cut by tunnels which penetrate the base of the mountains at right angles to the strike of the strata.

When the coal is thus exhausted above the natural drainage, or when the amount of available coal above water level will not justify the expense of a tunnel, the slope method is generally adopted, particularly where the angle of dip is great. The slope is always formed in the coal, except when the undulations of dip require it to pass a short distance in the overlying or underlying strata. In this respect, technically speaking, the slope differs from the oblique or underlying shaft, which penetrates the rocky strata to reach the coal; though generally a shaft is perpendicular, however the strata may dip. - In addition to these peculiarities of the Pennsylvania anthracite formations and the consequent form of the mines and methods of development, a singular feature of the colliery establishments is the immense and costly structures known as breakers. ' These are generally masses of heavy framework of great elevation and strength, and are used for the fourfold purpose of breaking, selecting, separating, and storing the prepared coal. The breaker is built near the mouth of the mine, and the coal cars from the drift, tunnel, slope, or shaft are elevated by machinery to the top of the breaker. Here the coal is dumped into a wide shute provided with bar or flat screens and platforms.

The coal is separated by passing over the screens and selected by the workmen on the platforms. The purest and best lump or largo coal is thrown into a bin provided for the purpose, while the second size, or steamboat coal, passes into a second bin; and the remainder, excepting the dirt and slate or impurities, is put through the breaking rolls, which consist of from two to four heavy iron rollers provided with steel or chilled cast-iron teeth. In passing through these, the coal is hroken into small pieces, and descends into a system of large circular screens which are constantly revolving, and which separate the coal into sizes known as pea, chestnut, stove, egg, and broken coal; and sometimes a larger size used for large ranges or heaters in hotels, puddling furnaces, etc. The sizes above this are steamboat and lump, which last is the largest, and generally used for blast furnaces, though the steamboat size is often mixed with the lump for this purpose. Formerly this preparation of anthracite was exceedingly wasteful, owing to imperfect breaking machinery, and a careless habit of crowding the whole mass, both large and small coal, through the breaking rolls without regularity or order.. It is estimated that 20 to 25 per cent, of the coal was thus lost.

To these defects must also be added that both pea coal and chestnut were wasted in "dirt banks" during the early days of the anthracite trade. Those old banks now yield a large amount of small or screened coal, the remainder being convertible into pressed blocks of patent fuel, or carbonic oxide gas as a fuel. The waste is now considerably less, as the chestnut, pea, and sometimes lime burners' coal is screened, and only the dust and impurities are rejected, which in well arranged colliery establishments do not much exceed 10 per cent, of the whole. Yet this does not include a much greater waste in the inside of the mines, where a large percentage of small coal is often left in the "goaf," and not less than one third of the whole bed is abandoned as pillars. At the anthracite collieries, where the imperfect systems of "post and stall" and "pillar and breast" are still in general use, not less than one half the entire contents of the coal beds is wasted or lost; and in some cases the waste is still greater. In comparison with the English bituminous mines, this waste is 25 per cent, greater than that of the longwall and 30 per cent, greater than the bord and pillar systems of mining.

The coal breaker was invented by a Mr. Batten, who appears to have conceived the idea from the crushing rollers used in Cornwall, England, for the purpose of breaking copper, tin, and other ores. His patent, however, was seriously defective, in not specifying or claiming the combination of the mechanical devices, instead of the direct application of the toothed rollers to breaking coal, while his patent fees were thought exorbitant by the colliery owners, and were successfully resisted. The invention ruined the inventor, while it has conferred immense benefits upon the anthracite trade. This method was introduced in 1844, before which time the coal was broken to sizes by hand hammers. To break the amount of coal now produced by one of these large collieries would require not fewer than 100 men, and in some cases 200 would be required. There are now more than 400 such coal breakers in use in the anthracite fields. The process is peculiar to the Pennsylvania anthracite mines, where the coal, owing to its great hardness, requires special preparation for economical combustion.

It is thought by some that this preparation could be more economically done near the great coal marts, where all the waste, except actual impurities, could be sold, because the coal dust thus wasted is the best portion of the coal. - The Pennsylvania anthracite collieries are not only modified by the peculiar structure of the coal measures, but also by numerous distortions and faults which often seriously interfere with mining operations. The form and character of those faults are as peculiar and varied as the litho-logical structure. Dislocations of strata and crushed graphitic coal are the predominating forms of fault, but the replacement of the coal by rock and slate or shale is also frequent in the upper and smaller beds; while small local slips and narrow dikes or walls of rock sometimes occupy cracks in the coal beds, but these do not penetrate above or below the bed. The great dikes and slips found in the English and some of the French coal strata are unknown in American coal fields, which, with the exception of the anthracite fields, are singularly free from faults and dislocations.

Bat the anthracite fields of Virginia and New England are still more seriously injured, and even partially destroyed, by faults resulting from excessive heat, violent lateral contraction, and the consequent contortion of the strata and pulverization or partial consumption of the carbon. These irregularities are important considerations in the establishment of collieries, as permanence and success depend greatly on the uniformity of the coal bed and the purity of the coal. These and other considerations have made the anthracite business more precarious and costly than the bituminous, and in all countries where anthracite is mined these peculiarities are observable to a greater or less extent. In addition to the cost of the great coal - preparing establishments, which frequently amounts to $100,000 or $150,000, the expense of sinking the pit or slope and opening the mines is also much greater than in the bituminous regions for corresponding depths. Both the measures and the coal are harder in the former than in the latter; and while the mining is conducted with but little powder in the one, the other requires immense quantities. Anthracite is almost exclusively obtained by blasting. At some of the mines more than 500 kegs of powder are used per month.

The value of these collieries ranges from $30,000 to $500,000 each, but the average value cannot be less than $100,000 for the 437 collieries in existence in 1871, at which 52,227 men and boys were employed. The United States census of 1870 makes the value of 1,550 colliery establishments of the country $86,087,251; while the wages paid the 93,805 men and boys employed is given at $43,647,-118. - Hitherto the greatest amount of the Pennsylvania anthracite has been mined from the outcrops of the beds, by drifts, tunnels, and slopes; but as this portion of the beds approaches exhaustion shafts become necessary to penetrate the interior of the basins. The deepest shaft yet sunk in the anthracite fields is the Dundee pit in the Wyoming field, S. W. of Wilkesbarre, which is 700 ft. deep; but it only penetrated the upper beds, when it was abandoned. The next in depth is the great Hickory shaft near St. Clair, in the southern anthracite field, which is 680 ft. deep to the Mammoth bed. Near the latter two large pits are now in progress (1873), which are each expected to penetrate 1.500 ft. to the same bed, and to cut nine or ten workable beds above the Mammoth. The depth of the slopes varies greatly; some of them have penetrated 900 ft. vertically and from 1,200 to 1,500 ft. on the inclination of the bed.

The large slopes are often 20 to 24 ft. wide and 7 to 10 ft. high, and provided with two hoisting ways and a double pump way, or a pump and a travelling way. The following table shows the number and condition of the anthracite collieries of Pennsvlvania:

The Great Open Quarry of Anthracite, Summit Hill, Mauch Chunk Mountain, Pa.

Fig. 1. - The Great Open Quarry of Anthracite, Summit Hill, Mauch Chunk Mountain, Pa.

Mammoth Coal Bed. a. The great quarry oft the Mammoth coal bed.

Fig. 2. - Mammoth Coal Bed. a. The great quarry oft the Mammoth coal bed.

The old Baltimore Mines.

Fig. 3. - The old Baltimore Mines.

English Coal Measures and Unconformable Rock.

Fig. 4. - English Coal Measures and Unconformable Rock.

Alleghany Coal Measures.

Fig. 5. - Alleghany Coal Measures. a, location of drift; a', improper location; 6, location of slope; b' location of tunnel; c, location of pit.

Incline and Drifts.

Fig. 6. - Incline and Drifts.

Plications of Anthracite Measures near Pottsville, Pa.

Fig. 7. - Plications of Anthracite Measures near Pottsville, Pa. a, Sharp mt.; b, Pottsville; c, Deep pits; c', Hickory and St. Clair pits; d, Mine hill; e, irregular axis; f, Broad int.

Drift with dip and strike of inclining coal beds.

Fig. 8. - Drift with dip and strike of inclining coal beds.

Slope, underground tunnel, and coal breaker.

Fig. 9. - Slope, underground tunnel, and coal breaker.

Slip Dike.

Fig. 10. - Slip Dike.

Change of Horizon.

Fig. 11. - Change of Horizon.

Trouble   volcanic formations.

Fig. 12. - "Trouble " - volcanic formations.

Section of Slope.

Fig. 13. - Section of Slope. a. travelling way: b, b. hoisting ways; c, pump way; d, pump. - 1. 1. legs; 2, centre props; 3, collar; 4, sill; 5, backing or laggins.

DISTRICTS.

No. Collieries.

No.

Shaft*.

Slope*.

No. Drifts and Tunnels.

Schuylkill.............

164

13

141

102

Northumberland.........

33

0

18

62

Columbia..........

8

0

7

4

Dauphin..........

4

0

4

11

Luzerne - East.....

80

46

21

68

" West

102

81

43

42

Lehigh District......

46

1

50

11

Total .......................

437

91

293

290

Some of the recent anthracite shafts are of very great size. Several near Wilkesbarre are more than 40 by 20 ft. in dimensions, but this is generally acknowledged to be an unnecessary size in square or oblong shafts, as this form demands timber for support, and the timber must be proportionately large and of great length. This is an element of weakness and danger, and at best only of temporary utility.

The natural decay of wood unfits it for use in pits. But the chief defect is in the form of the pit, and the English mining engineers long since discovered this serious objection to square or oblong pits, and substituted the round pit, in which brick, stone, or iron can be economically used to secure the sides of the shafts. Besides, this seems to be the only sure method of damming back the water, which in the timbered pits is allowed to enter the shafts and must consequently be pumped out at constant expense. But in circular pits all the water above the coal, and particularly the more abundant surface drainage, which is most seriously felt in the upper 300 to 500 ft., is dammed back with masonry or iron tubing. As the surface drainage always varies considerably in wet and dry weather, a portion of the pit is sometimes wet and sometimes dry, and this alternation, with the incident changes of temperature, induces decay when the pit is timbered, and replacement is dangerous and difficult. ^ The great size of the Pennsylvania anthracite pits is the natural outgrowth of the great size of the coal beds. Nine tenths of the anthracite mines are from beds varying from 10 to 30 ft. in thickness.

Mine cars of great size and of unwieldy proportions are used in many of them, with doubtful economy, since the most available systems of mining, known as bord and pillar and longwall, cannot be properly followed in steep-dipping beds with cars of greater capacity than one ton of coal each; yet the cars used in the anthracite mines generally contain from one and a half to three tons of coal, and weigh with their contents as much as five tons. They cannot be taken up the steep pitches by mules or be handled by the men; and this involves a second handling of the coal and some contrivance for getting it from the mines to the cars, which cannot leave the levels or gangways. Shutes are commonly used, but when the dip is too steep to admit the use of mules to draw the cars up to the mines, and too low for the coal to slide down a shute, great trouble and expense are involved. Besides, these systems of breast and pillar or post and stall mining are defective in many other respects. Some of the large anthracite pits are capable of producing 1 000 tons of coal per day; yet this has rarely been accomplished, from the difficulty of handling so many heavy cars at the top and bottom of the pit, or the greater difficulty of getting them to the bottom of the pit through a single level or double gangway, one on each side of the pit, to which the system in use, and the necessity of working the larger beds only, confine most of the anthracite mines.

But this production is exceeded by much smaller and deeper English pits, in which cars or bogies holding from 8 cwt. to one ton are used. In some of these deep pits a regular production of 2,000 tons per day is not unusual, though 250 to 500 tons is more common. - The late mining laws both of England and Pennsylvania require two openings for ingress and egress to each mine, so as to secure the safe retreat of the workmen in case of accident, and more perfect ventilation. Some of the most serious and fatal accidents have been occasioned by the absence of a second outlet; one of the most notable was the Avondale disaster, in the "Wyoming valley, near Plymouth, Pa., in 1871. This was occasioned in all probability (though the fact was never established) by the exceeding dryness of the timbers in the upcast portion of the pit, which was divided by a partition of wood. One portion of the pit was used for hoisting coal and the admission of air, and the other for the egress of the mine vapors. At the bottom of the latter a furnace was in constant use, the heat from which made the timbers like tinder, and the soot could not fail to accumulate, as in ordinary chimneys. A spark only was necessary to ignite the one or the other.

But in other cases, the burning of the structures erected over the pit's mouth, the destruction of a portion of the pit by explosion or caving, flooding of the mine by water, or the derangement of machinery, all point to the necessity of a second outlet from each mine, as a matter of common prudence. The methods of descending and ascending deep pits have been and still are very generally defective and insecure. In the great mining districts of the world, both in coal and metalliferous mines, the ladder and the hoisting apparatus are the alternatives. To ascend and descend a pit of 1,000 to 1,500 ft. on ladders is nearly a day's work, while descent or ascent on the cages is dangerous. The number of accidents caused by the falling of cages or cars in the anthracite mines during 1871 was 13; and this has always been a fruitful source of mining accidents, partly from the crowding of men anxious to be first at work or first at home, on the cages or into the mining cars. The mining laws of most of the great mining districts prohibit the use of unsafe cages, and the crowding of men on either the car or the cage; but these laws are seldom enforced.

The hoisting apparatus, elevators, or lifts used in hotels and manufactories are too slow for mining purposes; and though numerous safety cages have been invented, few if any are perfectly secure. Many "safety-catch" arrangements, however, are in use, which if kept in order would generally prevent serious accidents. The two most practical forms of clutches seem to be the "claw" and the "eccentric." The former are thrust out into the timbers or guides, and the latter hugs the guides on opposite sides when the rope breaks. One defect, however, of all such arrangements, very difficult to overcome, is that they sometimes act during the rapid descent of the cage, which in some cases is equal to the speed of a railroad train, and little short of the motion at the start in falling from a broken rope. Consequently all such devices are defective in pits, and the best cages are unsafe means of conveyance for the workmen. Yet on these, or still more rude and dangerous conveyances, or on ladders, ninety-nine out of every hundred miners depend for descent to and ascent from their work. In a few cases, during late years, "travelling rods" have been used with considerable success, though but rudely contrived and fitted up.

They consist of two perpendicular oscillating rods, generally of wood, placed side by side and parallel to each other in the travelling apartment of the pit. Some of these are simply provided with steps, without guards, while in others the rods have platforms securely guarded against danger. In other cases, however, a single rod is used, on which platforms are fixed at intervals, with corresponding stationary platforms in the rock; but the latter plan is much inferior to the former, in which the rods are so balanced that the power required to operate them is but little, while the single rod must be lifted with its weight of men, ascending or descending. In descending the miner steps on one of the moving platforms which comes to the top of the pit, and as this only remains a few seconds, during the slow motion of turning the upper centre of the operating wheel, he must be ready to step on without delay, though a failure to do so would not be dangerous. The motion may be five to ten strokes per minute without difficulty. Immediately on reversing the rod descends 8 to 12 ft., meeting a corresponding platform on the ascending parallel rod; on this the miner steps, and the platform he left ascends, and the one he is on descends.

Thus he steps from platform to platform and descends from 100 to 200 ft. per minute. In ascending the same rule is observed, except that the miner steps upon the ascending platform instead of the descending one; but whether ascending or descending, he is alternately now on one, and now on the other; and though 20 or more miners may be going up or going down at once, the balance is always nearly equal. The best mode of constructing these rods is to place them close together, with the platforms on opposite sides; and instead of two, four rods are preferred. In stepping from one platform to the other, the miners pass between the rods. In order to prevent accidents from carelessness or otherwise, the platforms should fit the compartments neatly, so that the men could not even by thoughtlessness endanger life or limb. In the construction of such means of vertical conveyance, in pits of great depth, iron or steel bands, links, or ropes could be judiciously made use of, connected on top by square links over a toothed wheel, making alternate reverse revolutions. - The methods of sinking pits have been considerably improved within a few years, by the use of new mechanical contrivances, or inventions in boring, blasting, and contending with water, quicksands, clays, or hard materials.

In blasting, the use of dualline is preferred by miners to other new explosive compounds, on account of its superior safety and effectiveness; while electricity is now generally used by experienced engineers both in sinking and tunnelling. It is not used, nor is it desirable, in ordinary coal or iron mining for the discharge of single blasts; but where the simultaneous discharge of numerous blasts is required, nothing but electricity is available. An experiment, which so far has proved successful (1873), is being made at the deep pits now in progress by the Philadelphia and Reading railroad company near Pottsville. This consists of boring a system of holes, about 20 in number, 300 ft. deep, in the bottom of the pit, by a set of diamond drilling machines. When these holes are completed in one pit the machines are removed to another. The holes are then filled with loose sand, and blasting with dualline and electricity is commenced by scraping out 5 ft. of sand to receive the explosive charge. Thus the alternate blasting and removal of broken material is continued, until the bottom of the holes is reached at 300 ft. The miners and drilling machines are thus constantly though alternately at work, and the progress is comparatively rapid.

But the experiment seems hazardous, because the sand in some cases hardens, and the second drilling is more difficult than the first. Silicious or acidulated water, with the concussion of blasting, solidifies the sand. A method has been invented by S. H. Daddow, of St. Clair, Pa., for sinking pits, square, oblong, or circular, to enable drilling machines of any class to be used, and to otherwise promote the safety and facility of sinking pits. It consists in a shield and platforms which provide for the use of three sets of men, and mining operations at the same time, instead of one set, as now practised, and facilitates the work in nearly equal proportion. The shield consists of a ring and platform of wrought and cast iron, strong enough to resist the effects of blasting, and arranged to protect the miners entirely from those at work above the shield. Thus the sinkers work below the shield, which follows them as they sink deeper; while on the top of the shield, which forms a platform covering the area of the shaft, a set of drilling machines are placed, which drill holes for the blasts, while the miners clean up the broken rocks from the preceding blasts. Over this first platform a second one is erected, on which the timbermen or masons work.

Trap doors are fixed in the shields for the passage of the buckets, and a tube for ventilation descending from the top of the shaft, so that the workmen could be supplied with both food and air even if the shaft should cave in; while in sinking through clays, quicksands, or soft material, the sides of the shield offer ample protection. For sinking through the upper clays, gravel, etc, or through marshes, rivers, or even a shallow sea, this shield is attached to the lower end of a pneumatic tube, like those now used for piers, water pits, etc, and sunk in the same manner, using compressed air, with pipes and air chambers to force out the water, mud, and other fluid material. When the pneumatic tube is safely anchored on a bed of rock, the sinking shield is detached and used for sinking, as in the former case, while the air chambers are removed out of the shaft, and permanent walls or cribbing of iron or wood inserted below the tube. When it is necessary to put in metal casing or tubing to dam back water, quicksands, or decomposing fire clays, such as are met with in some of the bituminous coal fields at great depths below the surface, the usual method is employed.

The casing is taken down the pit in sections and bolted together to form the tube at the bottom; and this may be done below or above the shield. When the surface water has been properly stopped and all the heavy springs dammed back as they are met, the water will not be difficult to manage with buckets, even when great springs or underground watercourses are met with. But when the accumulation of many streams descends to the bottom of the shaft, any great feeder of water might overcome both buckets and pumps. The purpose of such walling, cementing, and tubing is to avoid the use of pumps either during sinking or permanently, because the water can be drained more effectively. This method of damming back the water has not been used in the anthracite mines of Pennsylvania, and rarely if ever in any American pits, most of which are square or oblong, and both sinking and permanent drainage are effected by pumps, at great and constant cost. The best pump for sinking is that known as the Cornish bucket pump, with the column pipe larger than the working barrel, so that both the buckets and the clack valve may be drawn to the surface through the pipes, if necessary for repairs, in case of accident. The pump rods must work inside of the pipes in this plan.

This pump may be greatly improved for ordinary permanent lifts by reversing the above order and providing a working barrel of double the capacity of the pipes, and combining the plunger and bucket principle in the working barrel. Thus the down stroke forces one half the water from the barrel, and the up stroke draws the remainder. This is the cheapest, simplest, and most effective style of pump for all purposes, worked from the surfece. But most of the large collieries of the world are now drained by the common Cornish plunger or force pump, the principle of which is well known. Some of these are operated by complicated machinery, but the best are those in which the pump rods are connected directly with the steam piston of the engine, without additional gearing. These are used to force water 500 ft. high, but 200 to 250 ft. vertical height is far more economical and safe. Mining pumps of a new and far more effective style have been introduced during the last 10 or 15 years. They are direct-acting force pumps, but instead of being connected with the engine by rods, the steam is carried in pipes to the bottom of the mine, where both steam cylinder and pump are connected by a very simple arrangement, as a single piece of machinery.

The Allison and Bannan pump is generally used where pumps of this class are employed in anthracite mines, while the Cameron pump is used in England and this country for the same purposes. One of these has recently been placed in the mines at Bishop Auckland, England, with a steam cylinder of 26 in. and a pump barrel of 6 in. diameter, with 6 ft. stroke to each. This pump throws a steady stream of 120 gallons per minute up a vertical height of 1,040 ft. in a single lift, under a water pressure of 700 lbs. per square inch. At the close of 1870, 130 of these pumps were at work in the mines near Newcastle and Durham, England. - The raising of coal from deep mines is now almost exclusively done by cages, on the principle of the elevators used in hotels. These cages are moved with the speed of a railroad train. They are provided with " shoes," or projecting guide slots or holes, which move on or in guides of wood, iron, or rope, extending from the top to the bottom of the pit. These cages are in one or two stories, and carry one or two mine cars on each story. They are provided with rails corresponding to the track both at the bottom and top of the pit. The time occupied in shifting the cars and hoisting through 2,400 ft., in the Rosebridge pits, near Wigan in England, is less than one minute.

When the water is properly dammed back there is generally very little in deep pits; and when the mines are dry and dusty, as they very generally are, there is scarcely enough water to moisten the air and allay the dust, if properly distributed over the mines, which however is rarely done. But when the water is in excess, and not very abundant, a tank may be placed beneath the cage, which dips into the water and fills through self-acting valves at the bottom of the pit, and discharges by automatic arrangement at the top. This is simple, cheaper, and better than pumps in very deep mines, when the water is not excessive; but when it is abundant, the pump is the most available. The cages are now generally raised by means of two engines or steam cylinders connected directly, without spur gearing, to the cranks of the drum on which the rope is wound. The engines are connected with link motion, so that one is on the "live centre" or half stroke while the other is on the "dead centre" or full stroke, and are reversed at each ascent and descent of the cages, of which there are always two, one descending while the other is ascending. Round wire or steel ropes are generally used; but there can be no doubt that flat steel ropes are the best for deep pits.

These should be made of uniform steel, and composed of several round ropes combined, or served together with steel wire, and very carefully stretched and adjusted before they are put to work. Flat ropes work on or in grooved drums, and lap on themselves. Thus at starting, when the strain on the engines is the hardest, the diameter of the drum is the smallest, and much in favor of the lift; while the descending car and cage, which act as counter-balance, are on the larger diameter of the drum, because on this side the rope has lapped on itself and increased the diameter say two inches at each revolution, so that if the drum or groove was 10 ft. in diameter at starting the cage from the bottom, and the pit 2,000 ft. deep, its diameter would be about 20 ft. when the cage arrived on the top. Another very desirable method of elevating coal or water is the "pneumatic lift," now in general use to supply the new material to the top of blast furnaces, and in a few cases to elevate coal in pits. For very deep pits this seems to be an admirable method, and where a pair of circular pits are used, with brick and cast-iron lining, it is the most economical method, both in regard to first cost and permanent operation. The plan is very simple, but difficult to explain without elaborate engravings.

The elevation may be effected by means of suction or compression of the air, as now practised in the pneumatic despatch tubes. This mode of elevating coal or water may be extended to any practicable depth, or perhaps as deep as the English or French and Belgian coal basins descend below the sea level, without complicated machinery, and with perfect safety; while the power employed to raise the material supplies the ventilation, because the entire area of the pits can be used to supply air under pressure or vacuum. Thus compressed air may be used for all underground purposes, except the mere handling and breaking down of the coal, as machinery is successfully used for "undermining," which is the most laborious and costly item in mining bituminous coal; while in anthracite mines drilling holes for blasting is the most laborious part, and this also can be done more effectively and cheaply by machinery. (See Mining.) - The increase of temperature is the only great apparent obstacle to increased depth of pits. According to English experience, the temperature rises 1 degree for every 60 ft. of depth.

It appears that the old Kuttenberger pit, in Bohemia, was abandoned at 3,778 ft. on account of the high temperature at that depth; but this pit was sunk before the invention of gunpowder, when blasting was performed with lime, or the rocks were cut with picks and gads or "feather and wedges," and when mining science had made little progress and the best methods of ventilation were not understood. A Belgian coal pit has been sunk 3,411 ft., and one of the largest English collieries is in successful operation at 2,445 ft. The dangers, diseases, and hardships of the collier's life are not the result of deep mining, but of the rude and barbarous character of the mines, and the system of working. Even at the present day nine tenths of the mines of the world, whether of coal or of metals, are not only dangerously imperfect, but unworthy the scientific attainments of the age. In mines which are provided with proper means of ingress and egress, and are well ventilated and drained, the collier's employment is not remarkably dangerous or unhealthy; but this is the exception and the reverse is the rule.

The following table of comparisons shows the relative economy of production, and the ratio of danger between the different systems of mining during a period of three years ending 1869:

Pennsylvania Anthracite Shaft (section).

Fig. 14. - Pennsylvania Anthracite Shaft (section). o, pump and rods; b, pump apartment; c, c', hoisting apartments; d, travelling apartment; e, ladders. - 1,1, supporting timbers; 2, pump timbers; 3, 3, 3, dividing timbers; 4, backing plank.

English Circular Shaft.

Fig. 15. - English Circular Shaft. a, pump way; &, travelling way; c, c', hoisting ways; d, brick or stone lining; e, rock.

Travelling Rods.

Fig. 16. - Travelling Rods. a, basket platforms; 6, c, partitions and supports; d, rods.

Safety Shield and Platform.

Fig. 17. - Safety Shield and Platform. a, a, set screws; &, 5, drilling machines; c, c, cast-iron supports for wall; d, wall of brick or stone; e, pipe conveying compressed air; f, cement between walls and rock; g, rope; h, rock; k, flexible hose. - A, shield; B, temporary platform; C, timber for support of A; D, shaft after walls are in; D', shaft before walls are put in; F. bottom of shaft.

Underground Mining Pump.

Fig. 18. - Underground Mining Pump.

DISTRICTS.

SYSTEM OF MINING.

No. of tons raised per death from explosions by gas.

No. of deaths from explosions of gas.

No. of deaths in three years.

No. of tons of coal raised per death from underground accidents.

No. of tons raised per death from all causes.

Ratio of safety from explosions of gas.

Ratio of safety from underground accidents.

Tons of coal per capita per annum.

1. Northumberland, Durham, and Cumber.

land, England.............

Bord and pillar...........

4,738,471

7

249

352,863

133.310

100.00

67.98

387

2. South Durham...................

Bord and pillar.........

1,522,400

30

279

519,000

163,698

32.12

100.00

387

3. Manchester............................

Longwall..............

574,194

36

218

234,897

94,821

12.11

45.25

271

4. Yorkshire.............................

Mixed, chiefly post and stall..........

78.180

371

595

273,632

48,746

1.65

52.72

262

5. West Lancashire and North Wales......

Mixed................

124,739

192

521

157,565

45,969

2.68

3036

237

6. Midland District......................

Longwall............

1,908.250

12

182

305,370

125,818

40.27

5S.82

275

7. N. Staffordshire (Potteries).............

Bord and pillar........

104,166

168

316

265.150

55,379

2.19

51.08

233

8. S. Staffordshire (special for 30 ft. coal)..

Longwall..............

870,514

35

324

179,274

94,037

18.58

34.53

353

9. Southwestern district, including Coal.

brookdale..........

Mixed...........

1,438,461

13

213

154,545

87,793

3035

29.77

238

10. South Wales..........................

Post and stalls........

135.983

202

533

166.477

51,536

2 86

32.07

310

11. East Scotland.........................

Longwall & bord & pillar

1,320.791

17

135

380,567

166.321

27.87

73.72

291

12. West Scotland........................

Longwall & bord & pillar

2,302,136

8

120

259.395

153,475

48.58

49.98

285

13. Schuylkill Regions, Pa. (one year, 1871).

Breast and pillar......

200,000

25

101

55,000

50,000

5.00

10.00

250

The production of coal in Great Britain during 1871 was 117,439,251 tons, by 370,881 men and boys. In producing this large amount there were 826 accidents and 1,075 deaths; and 109,246 tons of coal were raised for each death, and one life lost to every 345 persons employed.

Table Of Accidents And Deaths In The British Mines Fob Two Yeaes

CAUSE.

ACCIDENTS.

DEATHS.

1870.

1871.

1870.

1871.

Explosions of gas.............

56

52

185

269

Falls of coal, rock, etc...........

402

426

411

435

Ascending and descending pits..

37

39

47

41

Accidents about pits............

81

79

82

82

Miscellaneous underground accidents, explosions of powder, etc.

174

161

186

176

Miscellaneous surface accidents.

80

69

80

72

Total....................

830

826

991

1,075

In the anthracite mines of Pennsylvania the number of deaths from all kinds of mining accidents during 1871 was 274, and the number of tons of coal mined per death 64,500. There were 52,227 men and boys employed in and about the mines, and one life was lost for every 190 employed. This great excess of fatality in the Pennsylvania anthracite regions is partly owing to the large size of the coal beds; but the chief defect is in the bad system of mining, and recklessness in regard to life. In South Wales (No. 10 of the preceding table) similar methods are employed and similar results observed, though the coal beds are not much if any larger than those of the Newcastle district (No. 1), and not as thick as the coal beds of Scotland (Nos. 11 and 12). Where the longwall and bord and pillar systems of mining are used, the best results are obtained; and where the post and stall and breast and pillar methods are in use, the worst results follow; though in the Staffordshire districts, where iron ores and fire clays or the thick coals are mined, the dangers are greatly increased, whatever system is used.

There are no data for comparing the mining casualties of the present with those of the past, in proportion to the number of employees or the annual production; but it is gratifying to observe that the ratio of deaths and accidents is constantly diminishing at the collieries of the great producing districts, notwithstanding that the mines are constantly becoming deeper. Moreover, the many causes of disease incident to the older mining communities, resulting from defective ventilation and the poisonous vapors of the mines, carbonic acid (black damp), carbonic oxide (sweet or white damp), sulphurous acid (powder, smoke, &c), soot, dust, and a general deficiency of pure air, are gradually disappearing. - The pay of colliers differs so greatly that it is not possible to give any regular price. In the anthracite regions laborers in 1871 were paid from $9 to $11 a week, and miners from $12 to $15; but most of the latter work by-contract, and earn from $15 to $20 a week, and sometimes $100 a month, and the cost of coal then ready for market, exclusive of royalty, is about $2 a ton; but the wages have been as low as $4 50 a week for laborers and $6 for miners, and the cost of coal less than $1 a ton.

At the English mines, miners' wages are even now much lower than at American mines, though nearly double the rates of ten years ago. The average cost of Newcastle coal during 20 years, on top of the pit, was 2s. 8 1/2d., and onboard at Newcastle, 5s. 6d., made up as follows: rent or royalty, 6d.; delivered in cars, 2s. 8 1/2d.; freight, 1s. 6d.; interest, 10d. In Yorkshire, Staffordshire, Lancashire, Scotland, and Wales the average cost of bituminous coal was 5s. 8d. during 1845, but during 1871 twice as much. During 1850 the number of the employees, men, boys, women, and girls, in the Belgian mines, and their wages, were as follows:

EMPLOYEES.

No. below ground.

No. above ground.

Wages in frs. above ground.

Wages in frs. below ground.

Men......

28,471

7,531

1.70

1.74

Boys.......

4,464

1,075

0.65

0.94

Women.............

2,274

1,771

.92

1.30

Girls...................

1,221

1,142

.56

.85

The great advance in the price of coal in England during 1871, 1872, and 1873 is largely due to the greater demand for both coal and iron, and the decrease in the hours of labor and increase of the wages of miners. The increase of collieries, and the use of machinery in mining coal, will without doubt eventually reduce the price of coal even below its former rate, without reducing the prices of labor to the mere pittance formerly paid in England, and still paid in France and Belgium, for underground work.