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Indiana University Studies 



by a hydraulic cylinder and piston or by a screw feed. A bit 

 is placed at the lower end of the rod and cuts an annular hole 

 in the rock as the drill is rotated. The point or end of the bit 

 is fed with chilled shot and is kept cool by water forced thru 

 the rods, the stream of water removing the waste cuttings from 

 the bit. The central piece left as the drill cuts down is called 

 the ''core". This solid core is the essential feature of this method 

 of drilling. It is the section of rock which is formed by the hollow 

 bit and rod as the drill advances. At intervals, usually after 

 drilling 10 feet, the rods are withdrawn by means of a hoisting 

 mechanism bringing with them the rock core, which is caught 

 and held by a self-locking "core lifter". The core is then re- 

 moved, the rods again lowered, and the process repeated until 

 the desired layer of stone has been penetrated. A careful study 

 of this ''core" will show the prospector the depth of the bed, its 

 thickness, and the character of the stone in the quarry. This 

 helps to determine whether or not the bed will justify opening. 



Since the motion of the diamond or chilled shot drill is a 

 rotary one, it follows that where electricity is available the 

 motor is the logical form of prime mover to use in working the 

 drill. However, steam can be used to turn the drill thru a system 

 of gears, and at present this method is in use thruout this district. 

 The facts shown by the drill core should not be taken as sufficient 

 evidence on which to open a quarry, for altho the thickness of 

 the stripping of overhang rocks and disintegrated material can 

 be ascertained with a fair degree of accuracy, yet if the drill 

 were set up over a pinnacle in the rock, a false impression of its 

 thickness would be obtained, and if the drill were driven into a 

 seam, the quarry might be abandoned altho much good 

 stone might really be available. Of course, a number of drillings 

 may be made, and only by chance would the same conditions be 

 found at each point of drilling, but it is a fact that several quarries 

 have been opened as a result of a single boring, and many quarry 

 sites have been abandoned on the same sort of evidence. Diagonal 

 drilling with the diamond drill is in use in iron mining operations 

 and is proving a success. This fact should be a strong recom- 

 mendation for its use in quarry prospecting. Diamond drills 

 can be driven at as high an angle as 72 degrees from the vertical, 

 and if such an angle were adopted in quarry prospecting the 

 distance between the seams as well as their width and depth 

 could be determined with a very fair degree of accuracy. If 

 the drill entered at this angle and at right angles to the direction 



