78 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



consists of a photographic device with a lead block base. 

 The apparatus was lowered over the core which had been 

 previously marked by the trepan and the lead block took 

 an impression of the core head while the needle inside was 

 photographically checked by special appliances. 



In Fig. 42 it will be seen that no clockwork or other 

 complicated mechanism is required, the strong, pressure- 

 proof box holding very little movable apparatus. This box 



Fig. 42. — Florin's camera device. 



is filled with water and inside suspended by rubber rings 

 is a simple photographic apparatus a. Below this is a 

 magnetic needle b, a phosphorescent disc c and an inter- 

 changeable lead base d. 



Staggered holes with gratings allow water to penetrate 

 to the interior in such a way as to counteract pressure 

 effects while preventing foreign bodies from entering. 

 Starting at the top we have the photographic apparatus 

 in the non-metalhc box in which is a small round and rigid 

 celluloid film covered with an emulsion of silver bromide 

 in gelatine, very sensitive to light and obtainable at any 



