176 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



photographic apparatus having already achieved some 

 remarkable surveys. 



The first interior photographic device was that of Oehman 

 in 1905 in which shadows of a needle and plumb bob oppo- 

 site electric light globes were recorded on a sensitized 

 paper. The first device for photographing the borehole 

 walls was that of Atwood in Wisconsin, in 1907. 



Atwood's Apparatus. — This, the first external photo- 

 graphic device for boreholes, was invented in 1907 by J. T. 

 Atwood of Wisconsin University. The camera a (Fig. 115) 



Fig. 115. — Camera, tripod and lowering reel. 



is mounted in the lower end of a watertight tube b, 5 in. 

 outside diameter and 43 in. long. Near the upper end of 

 the tube a plate-glass window with a mirror c behind it is 

 mounted so as to reflect the image of an object placed 

 before the window directly down the tube and into the 

 camera (Fig. 116). On each side of the mirror is mounted 

 an electric lamp d with a reflector, which sends the light 

 through the window and also prevents any light from 

 shining directly into the camera. 



