86 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



closed by switch s'. Motor P drives drill D through gear- 

 ing train G. When the apparatus is lowered into the hole 

 and the drill point strikes the bottom, the drill is pushed 



Plate V. — Dixon's gyrostatic core orientator. 



up and collar U closes the motor switch s' starting the motor 

 and driving the drill. 



Shortly afterward collar V closes switch s in the circuit 

 of the electromagnet E causing pricker M to mark sheet 



