3OO In and Around the Morteratsch Glacier : 



Disintegration behind the Surface of the Walls. 



For a distance of two or three metres from the entrance 

 the superficial disintegration of the ice can easily be followed 

 into its mass producing disarticulation of the grains and 

 intergranular fusion along with contraction. In the study of 

 this feature the stereoscopic camera is particularly useful. It 

 renders services which are not to be obtained from the simple 

 camera. A stereoscopic positive represents the ice exactly 

 as tJu two eyes see it, and being permanent can be studied 

 later. Moreover, there is often too little light in parts of the 

 grotto for the eye to be able to see anything in the short 

 exposure which suits it. The camera, whether stereoscopic 

 or not, can be set up and exposed for any length of time 

 which may be judged necessary in order to obtain a picture, 

 and this, if stereoscopic, is all that is required for study. 



The visible capillaries in the ice are tubes filled with 

 vapour of water or air which lay themselves along the upper 

 edges of the grains in the course of the intergranular melting 

 of the ice. When these tubes become smaller and contract 

 they often suffer segmentation and form a series of spherules. 



If the external surface of the wall remains water-tight we 

 can have the case of a grain in the middle of the massive ice, 

 which floats in the water of fusion which surrounds it. As a 

 rule, however, the grains are so closely packed that the grain 

 which would float is prevented, and, in place of doing so, is 

 able only to exercise the corresponding pressure on the grain 

 above it. 



In the interior of the grotto the ice has on the whole a 

 smooth surface and the discontinuities in the ice behind it, 

 which proceed from the disintegration by radiation, appear to 

 be arranged more or less in layers. When a grain loses a 

 superficial sheet of ice by melting, the water which appears 

 occupies a smaller volume than did the ice which has dis- 

 appeared, and the space vacated during the operation is 

 occupied in the first instance by aqueous vapour of low 

 pressure. If the ice-grain under consideration is situated 

 near the surface of the wall of the grotto where disintegration 



