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SUMMARY OF CURRENT RESEARCHES RELATING TO 



fig. 131. A is the piece of metal under examination ; B, the support; 

 C, the fine adjustment for focussing the objective ; D, the objective ; 

 E, totally reflecting prism ; F, the eye-piece ; G, a movable tube carry- 



£ 



ing the prism ; H, the tube carrying the eye-piece ; J, the illuminating 

 prism ; E, the iris diaphragm ; L, the condensing lens ; M, the dia- 

 phragm ; N, the source of light ; 0, the lens; P, the absorbing cells ; 

 Q, the photographic plate. The objective D is directed upward, so that, 

 if necessary, very bulky pieces may be examined ; moreover, it is only 



