Page:Transactions of the Provincial Medical and Surgical Association, volume 2.djvu/131

 extremity of the galleries to the nearest shaft. In this employment they enjoy a much purer air, and a much less constrained posture than will be their portion when they are a few years older. The occupation of the common miner, as formerly mentioned, consists essentially in breaking down the metalliferous vein or lode, and the surface of the bounding rock on either side, by means of the pickaxe and lever, and the more powerful arm of gunpowder. Where the lode and rock are not very hard, and can be excavated by the former, these only are used. This, however, is rare even in the killas districts, for any considerable extent; and the fact certainly is that, whether from the hardness of a part, or a whole rock or vein, or from the greater expedition of the process, by much the greatest portion of the galleries in the mines of Cornwall, is excavated by means of blasting with gunpowder. The process followed is the same as that adopted by the common quarrier. Holes are driven, occasionally, on every face of the gallery, above, below, and on either side, but much less frequently in the first of these directions. Generally, during the process of boring, the operator is seated; occasionally he is obliged to stand either completely or partially erect. When the gunpowder is deposited in the bottom of the hole, the upper portion of this is rammed full of fragments of rock, ore, or clay, by means of a metallic cylinder. This process of confining the powder is called tamping, and the cylinder, a tamping-bar. During its performance the gunpowder is occasionally ignited, and the operator killed or severely wounded by the explosion.