HAWORTH. | Detailed Geology. 99 
rock masses by ordinary processes, principally underneath 
the large piles of tailings and waste rock. These tailings 
piles cover such a large fractional part of the surface, and 
absorb water so readily from rainfall and the pumps, that 
they constitute a great cause of leaks back into the mine. 
Mr. McClaire in his investigations went underground to ob- 
serve the effect of such tailings piles. He was able to notice 
that roofs in mines usually were leaking water under large 
tailings piles, while roofs some distance removed were dry, 
which is a good corroboration of the return of surface water 
to the mines. ‘This leaves only about sixty per cent. of the 
total amount of rainfali over the 240 acres to supply the 
total amount of run off. It is not believed that sixty per 
cent. of local rainfall could be obtained from the ground by 
pumping, as forty per cent. is toosmall an amount to account 
for the surface run off and evaporation. ‘There is, therefore, 
a margin or surplus of ground water to come from outside 
the 250 acres. But this surplus is small; probably ten or 
fifteen per cent. | 
A similar attempt was made to estimate the amount of 
water pumped from the South Side mining land and to trace 
its ultimate disposition. Greater difficulties were found here 
than on the Mastin land, principally on account of adjacent 
land having so great an influence. Here the surface is al- 
most entirely void of vegetation, and probably more than 
half of it is actually covered with piles of tailings and rough 
stuff from the mines, so that the run-off from rainfall is 
greatly checked. 
Just south of the eighty acres the Cornwall company is 
Operating mines. Still farther south, and bearing north 
towards the east, a limestone area is encountered. Here, as 
usual, ground near the contact line between limestone and 
flint is badly broken and the surface very porous and capable 
of absorbing surface water unusually well. As has alreidy 
been stated in these pages, a part of the South Side land is 
very hard and compact, while other parts are particularly 
open and broken. Mr. McClaire’s estimate of the total 
amount of water pumped could be supplied by forty-five inches 
of rainfall on about 100 acres of ground. The proportion of 
