ClIAI*. II.
COMPOSITION AND USE OF MINERALS.
675
which takes place; when the gases generated by the explosion of gunpowder are diffuseda thick smoke fills the shaft or level. The following analysis shows the extent of impurityof the air in the places in which the men are employed.
From eighteen samples the summary of the analysis was, oxygen 17 067, carbonic acid085, nitrogen 82*848, and in one instance the quantity of oxygen was reduced to 14*51,and in another the carbonic acid was 0*23. These results exhibit a lessening in the pro-portion of the vital ingredient of the air from its usual per centage, 21, and an increase in adirectly noxious ingredient, carbonic acid gas, from 0*05, its ordinary amount, calculated toproduce effects sufficiently injurious to those who for hours together inhale such a fluid.
Ventilation is produced by the sinking of various shafts at short intervals, beneath thelowest levels, and establishing free communication between them as speedily as possible.But no method hitherto introduced is adequate to maintaining the air in a state of purity;every mine is more or less wet, as it constitutes a receptacle for the waters permeatingthe strata through which it passes.
The Adit is the drain through which the water, lying above its level, and a great part ofthat raised by machinery, is discharged. One or more of the deepest shafts are appro-priated as wells, from whence the water is raised by steam power, a preliminary processinvolving the greatest difficulty and outlay connected with the working of many mines.Such a well or pit at the bottom of the engine shaft is called the sump , and when the waterhas been so far removed as to admit of the workings being carried on in the lowest levels,it is said to be hi fork. Mines in slate are generally more wet than those in granite.
When the mine is situated near the coast, its drain or adit generally opens on the surface,at a point a little above the level of the sea, and when inland the deepest valley in theneighbourhood is the place of its discharge. In some cases a large common adit has beendriven a little above high water into the centre of an upland mining district, and the separateadits of the several mines opened into this general drain. In many mines a large quantityof water is constantly poured through the interstices and fissures of the strata, and it is oftenat a temperature so much lower than that of the air in which the miners are at work, thatthey are subject to very serious chills from this cause.
Ladders are the universal means of ascent and descent, the distance between the levelsbeing generally 60 feet; a single ladder in former times reached from one to the other, butthe most usual length at present is from 4 to 5 fathoms. In the perpendicular shafts theinclination is commonly such that the ladder may nearly traverse the breadth of the shaft ;from 18 to 21 inches in the fathom is the inclination which experience has determined tobe the best calculated to facilitate the progress of the miner, being that which enables himto stand upright on the ladder with the leg clear from the stave above, so that the effort isdivided between the upper and lower extremities. The distance between the stavesis generally 12 inches, in some old ladders they were 14 inches apart, but 10 inches isfound the best for facilitating the climbing, by which one-fourth of the labour isestimated to be saved. The staves are of wood, though iron is in some instances preferred,m others it becomes slippery and rough from the corrosive action of water impregnatedwith copper, &c. Each ladder usually terminates on a sollar or platform, which leads tothat below, which is generally placed parallel to that above ; trap doors are providedover each man-hole to prevent accidents, but closing them obstructs the free ventilation.
The principal tools used by the miners are picks for working the rocks, borers and malletsfor making the holes for blasting; these are often sent up and down in the bucket ( kibble )in which the ore or rubbish is drawn to the surface, but the miner very commonly carries withhim from 10 to 20 lbs. weight of tools, there being a constant necessity for hardening andsharpening them, which is done at the smith’s shop ; in some mines this is established un-derground, which is very advantageous, the weight of coal sent down being only one-fortiethof that of the tools sent up.
The dress of the miner is of woollen, consisting generally of trowsers, shirt, and jacket;he does not wear stockings, but puts on a pair of thick shoes, and covers his head with astrong felt cap, hemispherical on the crown, and broad-brimmed, about 2 pounds in weight;on this he usually sticks his candle by means of a lump of clay, attaching another to abutton. These habiliments are, unless the miner lives near at hand, usually kept at themines in the changing-houses, where the ordinary dress is left until he comes up from hiswork.
I he great body of the miners underground are employed in excavating the rock,whether for the sinking of shafts, the driving of levels, or the removing of the veins ofore, which operations require the almost constant application of the explosive force ofgunpowder. The greatest part of the work consists in beating the borer, that is, in drivingan iron cylinder terminating in a wedge-shaped point, by blows with a heavy hammer(mallet), whilst it is turned by another hand. The necessity or advantage of makingthe hole in a particular direction often constrains the miner to assume every variety ofposture; he is even compelled at times to lie on his side. When the rock hasbeen bored to a sufficient depth, the charge is introduced and rammed down with a
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