The cost of sinking is in proportion to the size of the shaft and the hardness of the rock: much more, however, depends on the latter than on the former. In the softer strata, a shaft 10 by 20 may be sunk for 200 dollars per linear yard, when the wages of miners are about $1.50 per day; but in the harder metals the cost of sinking the same sized shaft will be over 300 dollars per yard. As an estimate, however, we do not think a shaft could be sunk 1000 feet through the anthracite measures in the centre of any basin for less than an average cost of 300 dollars per yard, independent of the cost of pumping and hoisting and of the material used. It depends, also, irrespective of hard ness, on the dip of the measures where the shaft may be sunk. As a general rule, it is easier to sink in the centre of a basin, where the strata are comparatively flat, than on the dips of the measures, where the strata have a high inclination, since it is more difficult to advance against the ends of the strata than to go through or across them.
Sinking is more costly in the measures of the anthracite coal-fields of Pennsylvania than in the bituminous coal-fields of the West or in the English bituminous coal-fields, since the metals in the former are much harder than in the latter. It seems to be a
characteristic of the anthracites generally; and we have no doubt that the greater heat which accomplished the change from anthracite to bituminous converted the rocks from a ferruginous or soft sandstone to a crystalline or more silicious and flinty nature, since the stratified crystalline and sub-crystalline rocks are harder than the upper sedimentary.
But, while the cost of labor in sinking is less, the actual cost of putting down a shaft in the deep bituminous basins is generally much greater than it is in the anthracite basins, owing to the open nature of the measures, and the immense quantity of water which they contain. In many cases the cost of sinking 1000 feet in the New castle coal-field has been over 1000 dollars per yard. We do not think the cost of sinking in any of our anthracite basins can exceed $500 per yard as the full expendi ture, if proper precautions are taken.