METHOD OF ATTACK. 



If we leave out of sight those mines, which are worked by the Government 

 on modern system, and the coal-mine in Takashima, then we find, that the 

 deposits are exclusively attacked by adits, as the machinery, requisite for the 

 sinking and working of deep shafts was formerly entirely unknown. In order 

 to prepare the working of a vein either an adit was driven along its strike, or 

 where the vein was sufficiently known and the locality favorable, the connection 

 with the surface was effected by a cross-cut. As soon as all the ore above this 

 horizon had been extracted, then a second adit had to be driven lower down and 

 so on. The extent of these adits is sometimes quite considerable — until about 

 10,000 feet — and we can imagine that such a work, carried on without the aid of 

 blasting powder, must have demanded, not only a large expenditure, but also 

 an enormous length of time. We are therefore in the abandoned mines still 

 able to estimate the richness of the ore deposit worked by the length of the 

 adits ; the greater the obstacles, which were overcome in order to get at the 

 ore, the richer the latter must have been. Of course other agencies, which can 

 now no longer be ascertained, may have had some influence, for instance: cheap 

 wages, compulsory labor, comparatively high value of the metals extracted 

 etc. When finally a point had been reached, where a still lower adit, 

 either on account of the configuration of the soil, or on account of the expense, 

 did not appear practicable, then the working was continued below the water- 

 adit as far down as circumstances would permit, and for hoisting the produced 

 ores as well as the water up to the level of the adit no other motor was employed 

 than the human hand or foot. 



The depth, which was reached below the level of the adit, depended of course, 

 on the one hand on the volume of water to be met with, on the other hand on 

 the quantity and quality of the extracted ore. Even under the most favorable 

 circumstances, a time must come at last, when the outturn no longer covered 

 the expenditure on winning, haulage and drainage, that is, wheu in the then 

 state of mining science it became necessary to abandon the mine. I mj-self 

 know several mines, which have been abandoned evidently for no other reason, 

 and I am convinced, that a still larger number are only waiting for the moment, 

 when modern engineering shall have aroused them from their centenary sleep, 

 again to yield a good profit. Under favorable circumstances, depths have cer- 

 tainly been reached, which, considering the absence of all aid from machinery, 

 must be declared considerable; the Innai silver-mine is for instance yet worked 

 fully 700 feet, the Eeishi copper-mine about 800 feet below the level of the 



