EXCAVATING MA< 'MINKS AM> !:'< K 1>I:1LI-S 



B 



the drill, and the power is better utilized ; (2) once the ma- 

 chines work easily they do not require continual refiairs, and 

 (3) in driving holes of large size the interior nucleus is taken 



PlO. 13. Column Mounting for IVr<Miloii Drill : li 



it rrlll Co. 



away intact, thus reducing work and increasing the sne<-<l -f 

 drilling. Kot.irv drills ;m- extensively usod for geological, 

 mining, well-driving, :ind ]>roperting purposes : lint Uioy are 

 vrrv seldom -tii|ilM\cl i:i tunnels in Amerir^ although 



