COLLIERY 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 collier- ies and salt works;" and upon certain condi- tions they were to be gradually emancipated, while others were prevented from coming into such a state of servitude. Even after the gen- eral 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 em- ployed 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 dis- tance 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 pro- hibited from working in the British coal mines. In Belgium, however, both women and chil- dren 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 con- stantly 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 FIG. 4. English Coal Measures and TJnconfonnable Bock. 1, 2, 8, &c., pits ; a, coal measures ; 6, Permian ; c, cretaceous, &c. ; d, slip dike ; e, trap dike ; g, trap dike ; &, Devonian ; t, Silurian ; #, Cambrian ; m, gneiss ; ., granite. depth, however. In many cases these pits pen- etrate the overlying Permian formation, be- neath which most of the carboniferous forma- tions 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 be- neath 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 be- low 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 doubt- ful 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 doubt- less be continued until the deep coal beds, re- posing 10,000 to 20,000 ft. beneath the sea, will be won and worked. In the great Ameri- can bituminous fields mining operations are much more diversified than in the bituminous fields of Europe. In the Alleghany and cen- tral coal fields the carboniferous rocks are the latest and highest geological formations ; con- sequently 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 de- veloped 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
