﻿M. A. Heim on Glaciers. 493 



the night, remained between 0° and —2°, and only rose a little 

 above 0° in the afternoon. In the first two cases the circum- 

 stances were similar to those at the surface of a glacier ; in the 

 third, more like those which operate on the internal ice of it. 



In each case I obtained a mass of ice apparently pretty com- 

 pact ; only a part of the fissures were still visible, though cer- 

 tainly not distinct. I could perceive no difference between its 

 appearance and that of the surface-ice of a glacier in the early 

 morning, before the ablation commences — at least, as far as I 

 still had the latter in my memory. On applying a little force, 

 the whole could be severed by the hand into its grains. Placed 

 in the warm room, or in the midday sun, the network of fissures 

 became somewhat more distinctly visible, and the grains could 

 now be more easily separated. Their surfaces had no longer 

 the form of conchoidal fracture, but were rough with irregular 

 elevations and depressions, exactly as in the secondary capillary 

 fissures, except that the unevennesses were finer and more nu- 

 merous. 



In these experiments, immediately after the breaking, con- 

 choidal surfaces only were seen; after regelation and partial 

 soaking had operated, only capillary fissures of the second order. 

 Because all these processes take place simultaneously in the gla- 

 cier, therefore we find also their effects together in the glacier- 

 grain. 



From the observations adduced it follows that the secondary 

 fissures originate from the primary by a secondary process, which 

 can be no other than regelation and soaking, because no other 

 intervened. Under the given circumstances, these processes 

 produce a wrinkling of the surface in the originally conchoidal 

 (in the glacier, flat) capillary fissures. Some experiments for 

 the purpose of deciding whether it was more the one process or 

 the other could be brought to no further conclusion. 



On the banks of the Havel and of the Muggelsee, near Berlin, 

 I found in the thawing crust of ice a division into irregular ver- 

 tical prisms (often trilateral). The ice had been formed during 

 a fall of snow. The prisms were partly separated by interspaces, 

 and partly adherent ; but the surfaces of nearly all of them were 

 finely wrinkled, reminding one of the secondary capillary fissures. 

 Prom the infiltrated water produced by the melting, furrowed 

 surfaces also occurred, which must not be confounded with the 

 plaited ones. 



The tray-shaped granular ice plate obtained in the experiments 

 could, within certain limits, be bent exactly as is the case 

 with the granular plates which, on hot summer days, can often 

 easily be separated from the borders of the crevasses and parallel 

 to them (reminding one of itacolumite). When thus carefully 



