Glacier fi of the Alpsi. 79 



rough and unequal ; a part of the crystals were broken into two, 

 and others, almost untouched, formed projections to which there 

 were corresponding hollows in the opposite surface. I sounded 

 the opening with my axe to a depth of 6 feet ; the fissure ex- 

 tended to only 4 or 5 feet, and gradually diminished to this depth. 

 Its examination clearly demonstrated the influence of the atmo- 

 sphere, and the effect of a high temperature. At 11 feet distant a 

 second fissure was formed in a direction exactly parallel to that of 

 the first ; I found it to be 6 feet deep. Afterwards I have often 

 observed this phenomenon upon the glacier of Aletch, from the 

 Elsenhorn to the lake Morile. I have seen three fissures take 

 place in an afternoon. Some of my guides had more than a hun- 

 dred times witnessed this operation. The crevices are formed 

 during warm days only ; and generally previous to a change 

 of weather. None of them are formed during the night, or in 

 winter ; but I have observed, on the contrary, that they con- 

 tract during the night, and completely disappear in winter. 



" During the whole period of my stay on the inferior glacier 

 of the Aar, we were awoke every night, twice or thrice, by the 

 subterranean noises which proceeded from the interior of the 

 glacier. Twice the bed itself which we had dug in the glacier, 

 and which was lined with slates and moss, was violently shaken 

 by jolts analogous to those which I had observed during the 

 formation of fissures ; but the shaking appeared so deeply seat- 

 ed, that we could not for a moment entertain the idea that any 

 rent or crevice would open at the surface. We heard and felt 

 directly that the effect had taken place from below upwards. 

 The noise was obtuse, of a particular nature, and was commu- 

 nicated to the atmosphere through the medium of the crystal- 

 line mass of the glacier. We have never found in the morning 

 a new crevice completely opened. I have heard the same sub- 

 terranean noises during the nights which I passed on the glacier 

 of Grindelwald, and behind the Finsteraarhorn ; but I have 

 never heard any of these dull subterranean noises during the 

 day, in my excursions on the glaciers. I have seen an inferior 

 crevice when I penetrated under the glacier of the V'iesch. It 

 was at least 5 feet wide below, and appeared to wedge out above 

 at a height of from 12 to 20 feet. I have never been able todis, 

 cover in this place, at the upper surface of the glacier, any fissure 



