4t4 



BORING 



rods, which is arranged to be always the same. The diamonds work their way by 

 steady and gentle attrition. 



These machines will bore holes from one to three inches in diameter. 



The advance, per minute in pure Mount Cenis quartz equalled 2J inches, in 

 granite about 2 inches, and in very hard calcareous dolomite 3 inches. 



The diamond machine shown by figs. 181 and 182 has lately been perfected by 

 Messrs. Appleby and Beaumont. 



The boring bit with diamonds set therein is exactly similar to that used in the 

 machine described, but the boring machinery is of a different description. This 

 machine is worked by ..:i independent engine, and driven by leather or other belts, 

 the circular motion given to the boring rods being conveyed by bevel gear. To this 

 machine appliances are attached for the driving forward of the lining tubes. This is 

 done by means of a series of weights N attached to a chain passing round the wheel M, 

 and connected to the sliding clutch g ; this is made to press upon the tubes. At the 

 same time an ordinary chisel is attached to the boring rods and worked from the table 

 A A, the rods passing down the centre of the tubes. 



182 



The dUbris is washed out at times by means of the pump fixed upon the machine. 



After the lining tubes are made secure and water tight (it being an essential point 

 that all water forced down the boring rods should come up on the inside of the lining 

 tubes, so that all washings or indications of change of strata may be at once noticed), 

 the diamond drill is introduced and boring proceeded with in the u$ual manner. 



The rods are drawn by means of a chain passing over shear legs about 45 feet high 

 and wound upon a drum fixed on the machine. The rods are unscrewed in lengths, 

 and placed on one side of the machine. 



The rods, by this system, are seldom drawn, except for the purpose of extracting the 

 core made ; the core tube being usually about 14' 0" long, with a small spring at the 

 bottom for the purpose of retaining the core while drawing the rods. The cores made 

 in these machines are usually from 1 inch to 1J inch in diameter. 



