Examination of Mines. 27 
of the vein, and dg hi and jk are drifts driven on the 
strike of the vein. 
To estimate the total tonnage of ore in sight of this 
mine proceeds as follows: Sample the three sides ab, bf 
fd, calculate the superficial area in feet of the side 
FIG. 14. 
Cross-Section Through Shaft bl Showing Formation, Class 
of Ore Deposits, Width and Dip of Vein. 
abfd and multiply this area by the average width of vein 
in feet (as determined from the several measurements 
made when sampling the block) ; the product equals the 
