312 



REPORT ON NATIONAL MUSEUM, 1886. 



SiiUivau diamond-poiuted drill and the Ingersoll impact drill are used 

 for gaddiug. The bottom holes are usually drilled to a depth equaling 



^Val•(hvt'll ili:miitlin;i; nuicbiue. 



about one-half the width of the block to be extracted, though this 

 depth, as well as the frequency of the holes, must necessarily vary with 

 the character of the rift of the rock. 



(4) SANDSTONE QUARRYING. 



In the quarrying of the Triassic sandstones at Poitland, Conn., the 

 channeling machine is also used to some extent, but the prevailing 

 method of loosening large blocks is by deep drill holes charged with 

 heavy blasts of powder. These holes, which are made by a crude ma- 

 chine driven by cranks, like an ordinary derrick, are 10 inches in diam- 

 eter and about 20 feet deep. Into these are put from 25 to 75 pounds 

 of powder, contained in a flattened or oval tincaunister, with the edges 

 unsoldered and closed at the ends by paper or cloth. This is placed in 

 the hole in such a position that a plane passing through its edges is in 

 line with the desired break, and fired. In this way large blocks are 

 freed from the quarry, and these are then broken to any required size, 

 as follows : The workmen first cut with a pick a sharp groove some 4 to 

 8 inches deep along the full length of the line where it is desired the 

 stone shall break. Into this groove are then placed, at intervals of a 

 few inches, large iron wedges, which are then in turn struck repeated 



