PHOTOGRAPHIC METHODS 



197 



opening over the controller. The standard dry battery 37 

 in carrier 39 bearing on plunger 38 presses its central stud 

 on to the contact bolt 21. 



The insulation rod 59 (Fig. 5, Plate XII) is attached 

 when the instrument is in use and coupled to the drill 

 rods or rope for lowering. Before making the survey 

 the device is taken to a dark room where the two carrier 

 tubes are taken out and uncoupled and record strips of 

 bromide printing paper are fitted to the clinometer and 



Magnei-i'c 

 Needle 



Inside View from above of Compass Apertures and Needle 

 Fig. 133. — Inside view of compass apertures and needle from above. 



E 



No.l 





±_1. 



(Daiutny^^' 2^J (Oaiumyi^-I 



(c) 



Kh) 



No-2 No. I 2 ; 



(Daiurn) (Dcrlum) 





90° 45° 0° 45° 90° /J5° 180° BS" 90° 



id) 



Fig. 134. — Compass record. 



compass drums. The datum record from which deviations 

 are measured is arranged in the dark room, this being a 

 standard datum such as the horizontal instrument casing 

 with the controller end toward the magnetic north. Now 

 set the record strips with controller to give one exposure and 

 reassemble the carrier tubes in the casing. After time 

 sufficient for exposure the controller automatically stops and 

 it is taken to the hole to be surveyed when the controller is 

 reset. The eyed plug 55 is now unscrewed and the carrier 



