170 Dr Martens on (he Glaciers of Spitsbergen. 



the ice, is a fact well known to all who have travelled in the 

 Oberland.* The formation of such crevices maybe reasonably 

 assigned to the alternate contractions and dilatations of those 

 masses which, during the long winters of Spitzbergen, are, in 

 all probability, exposed to a cold of — 40° C, while, in tbe sum- 

 mer, they are suddenly surrounded by an atmosphere whose 

 temperature is always above zero. The surface is then heated 

 more than the subjacent parts, the places covered with snow 

 less than such as are free from it ; hence, unequal dilatations 

 followed by continuous melting throughout the mass. Hugi 

 has often seen these ere vices forming under his eyes. Re- 

 specting one of them, he gives the following details : — " I was 

 one day walking over the glacier of the Unter-Aar, about three 

 o'clock in the afternoon. The heat was very powerful ; all of 

 a sudden I heard a peculiar noise. I had scarcely run thirty 

 or forty paces in the direction of the sound, when I felt the 

 glacier tremble under my feet several times ; at the same mo- 

 ment I saw that it was rending asunder. The fissure often 

 advanced from ten to twenty feet in an instant : I was scarcely 

 able to follow it. For a moment at a time it seemed about 

 to stop, or rather its progression was very slow ; but the en- 

 tire mass seemed to tremble, and the rent continued to length- 

 en. Several times I ran on before it, tbat I might lie down 

 on the glacier in the place where it must pass. Once I was 

 violently shaken, and the ice split beneath me. In this man- 

 ner I followed the rent for a quarter of an hour, as far as a 

 central moraine, Avhere it stopped. The breadth was an 

 inch and a half ; its inner surface, rough and unequal, expos- 

 ed to view crystals of ice, partly broken, partly torn asun- 

 der ; its depth did not exceed four or five feet. A few days 

 after, I visited the glacier a second time : the rent was six 

 inches wide, and its depth considerable. A new fissure, pa- 

 rallel with the first and six feet deep, had been formed in my 

 absence." t 



Many causes contribute to enlarge these crevices. In the 

 first place, the weight of the ice beneath ; then the water which 



* Ebel ; Manuel du Voyageur en Suisse, t. ii. p. 580. 

 t Hugi, 1. c. p. 354. 



