OPTICAL METHODS OF BORE -HOLE INVESTIGATION 



•'•■mimm: 



33S 





Fig. 6. Photographs of rock samples. 1 — sandstone in ordinary (left) and infra-red 



(right) light; 2 — dolomite (same conditions of photography); 3 — sandstone without 



magnification (left) and ten -fold magnification; 4 — sample of dolomite with lateral 



illumination (left) and direct illumination (right). 



