GRANITE QUARRYING. 69 
insignificant matter, but as the quarry deepens it assumes importance. 
Where the quarry stands at some elevation the drainage is easily 
disposed of by ordinary piping or siphoning, but if the quarry bot- 
tom lies below the level of the surrounding tract and if the drainage 
exceeds the needs of the boilers, pumping must be resorted to; but 
even in such places there must be some available stream or shore 
to carry off the water. The amount of pumping requisite varies 
greatly. 
Water supply. — When the needs of the boilers exceed the amount 
supplied by the drainage, neighboring springs or brooks are resorted 
to. On small islands that are without streams or copious springs 
the question of water supply in large quarries is a serious one. At 
one of the Crotch Island quarries water has been brought from 
Stonington, a mile distant, at an expense of $110 a month, and at the 
High Isle quarry water is obtained by pumping from accumulations 
in the old quarry pits on Dix Island. This required 3,900 feet of 
3-inch pipe. In order to obviate such outlays bored wells are being- 
resorted to, by means of which it is expected that the entire drainage 
of these islands will be made available. As explained on page 38, 
it is only the joint and sheet structure that makes granite a source 
of water. The subject of well boring in granite will be discussed in 
a paper to be published by the United States Geological Survey." 
If well boring should fail to yield an adequate supply to island 
quarries, the condensation of sea water could still be resorted to, as 
in ocean navigation. 
Use of explosives and wedges. — At no point in granite quarrying 
is more experience and judgment requisite than in the use of explo- 
sives. The selection of the place for blasting, the size and shape of 
the hole, the selection of the powder, and the size of the charge are 
all matters requiring careful consideration. The thickness of the 
sheet, the proximity of joints, the vitreousness of the stone, its rift 
and grain structure, the physical and mathematical laws governing 
the action of explosives, and the direction in which the quarryman 
desires to split the mass are all factors in each problem. 
The mathematics of the subject will be found treated in a recent 
book by Daw, 6 and a general description of quarry methods will be 
found in a report by Walter B. Smith. 6 ' 
The practice of foremen in the thirty principal granite quarries of 
Maine, as explained by them to the writer, was found to be as follows: 
Vertical blast holes almost as dee]) as the thickness of the sheet are 
"Bowman, Isaiah. Well-drilling methods: Water Sup. and Irr. Paper (in preparation). 
h Daw, A. W. and Z. W., The blasting of rocks in mines, quarries, and tunnels, etc.. 
pt. 1, London. 1898. 
c Methods of quarrying, cutting, and polishing granite: Mineral Industries: Eleventh 
Census. 1892. pp. 612-618; also Sixteenth Ann. Kept. U. S. Geol. Survey, pt. 4 (1894-5), 
pp. 446-456. 
