108 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



Maas Method: Hydrofluoric Acid with Gelatine. — 

 In this method a small glass tube about 6 in. long by a little 



GELATINE 



THERMOS 

 CASING 



Fig. 58. — Two-circle goniometer to measure inclination and direction o-f drill 

 holes. {After E. E. White.) 



over 1 in. in bore is used. It holds HF in one end and has 

 gelatine in the other holding a small compass. To obviate 



