GRANITE QUARRYING. 71 
(rated in fig. 3, diagrams A, B, and C. The case without rift or 
grain is marked I), and the hazardous one X. 
The blast holes are usually " lewis holes,' 1 which consist of two or 
three contiguous drill holes, with the intervening rock chiseled out, 
or,, where less force is required, " knox holes," consisting of a circular 
drill hole, with two diametrically opposite lateral vertical grooves. 
The drill holes may be made divergent below. The " channels " are 
about 4 feet wide and are made either by drilling blast holes in zigzag 
order, which are fired singly in diagonal order, or by drilling holes 
on both sides of the proposed channel in close order; or else the 
channel consists of a single row of contiguous drill holes. This prac- 
tice is found more economical than that of using a regular channeling 
machine. When the stone is delicate, as in the Hallowell quarries, 
powder is used sparingly or not at all. In the latter case channeling 
is done in two directions at 90°, and the operation is completed by 
splitting by wedges in the third. (See fig. 3, diagram H.) 
At the Long Cove quarry of Booth Brothers and Hurricane Isle 
Granite Company (p. 128) mining is resorted to. Shafts and cross 
tunnels are blasted out on the plan of an inverted T ( T) and large 
quantities of powder are exploded in the ends of the horizontal 
parts, in order to loosen a great mass of overlying rock. 
After the block has been loosened by methods A, B, or C, it is 
broken up into minor blocks by " splitting." As is well known, split- 
ting is now done almost entirely by the use of pneumatic plug drills. 
The holes are 3 to 4 inches deep, three-fourths inch in diameter, and 
a few inches apart. Every few feet a deeper hole is drilled. Iron 
wedges are thea very gradually driven in between steel side pieces 
called " feathers." 
A difference is found in blasting and splitting granite in winter and 
summer. A low temperature increases its cohesiveness, but, probably 
in connection with water, increases its fissility where the " rift " is 
feeble. 
It is reported that in quarries in Finland the expansive power of 
freezing water is regularly used in splitting. This is in line with the 
ancient Egyptian use of the expansion of w 7 et woody tissue. A 
method of blasting in use in some of the English coal mines by means 
of the expansion of slaked lime may be susceptible of adaption to the 
quarrying of the more delicate granites." 
In this connection should be mentioned the method recently 
adopted in the granite quarries of North Carolina of developing an 
incipient sheet structure by the use of high explosives followed by 
the application of compressed air. (See footnote, p. 37.) 
a See Mosley, Paget On a new method of mining coal:- Jour. Iron and Steel Institute, 
London, 1882, pp. 53-62. 
