78 Professor ITugi's Ohservat'tons on the 



year adds to the grains a new stratum ; thence the increase of 

 the whole mass, its rupture into crevices, and the observed ex- 

 pulsion of foreign bodies. 



" In proportion as a glacier of the first kind (and not of the 

 second) receives increase at its upper surface, it generally dimi- 

 nishes ac its lower ; yet it exhibits irregular periods of increase 

 and extraordinary meltings. The inferior melting appears to 

 follow a more uniform ccjurse than the superior increase. 



" Whilst the mass is granulated, it does not form any crevice 

 at its surface. The heat of the day, and of the summer, easily 

 loosens all its parts without breaking them ; but, by a long suc- 

 cession of contractions, moistenings, and expansions, the gra- 

 nular mass begins to crystallize togethei", each grain presents 

 determinate faces, and encases itself between the grains which 

 surround it : in a word, we perceive the formation of the sys- 

 tem of interlacement of gfains of which we have spoken above 

 (see article on Glaciers in last Number), and which consolidates 

 from that time more and more. The grains are no longer isola- 

 ted, but conjoined into a compact mass, which forms the glacier. 

 Afterwards the heat has no more the power of decomposing the 

 mass into its grains, but of expanding it chiefly at its surface. 

 The resistance opposed by this mass to the dilatation is soon 

 violently overcome, and it rends. 



'' One day being on the inferior glacier of the Aar, during an 

 intense heat, at three o'clock f. m., I heard a very peculiar noise, 

 I advanced rapidly from 30 to 40 paces, from the side where the 

 noise was heard ; I felt the mass of the glacier shake by jolts 

 under my feet, and I soon discovered the cause. A fissure was 

 formed in an instant, the aperture was elongated from 12 to 20 

 feet, so that I was unable to follow its formation. Sometimes the 

 operation seemed about to cease, and the mass separated itself 

 very slowly; then again the fissure continued to open quickly, and 

 by jolts. Many times I ran forward in time to see the separation 

 taking place under my feet. I followed in this way the formation 

 of the fissure over an extent of almost a quarter of a league, even 

 to the border of the glacier, where it stopped. The fissure open- 

 ed at first under the first concussion about an inch and a half, 

 but afterwards it again contracted, so that its breadth did not 

 attain to more than an inch. The interior of this fissure was 



