Report of the Researches ofM, Agassiz. 163 



Now that we were somewhat acquainted with the annual ab- 

 lation at a variety of points, we wished, moreover, to ascer- 

 tain what was the amount of the daily ablation. A stake in- 

 serted in the ice, at the distance of some hundreds of feet 

 from the Hotel des Neuchdtelois, upon the band of the Lauter- 

 Aar, served for these experiments. We surrounded it with 

 some flag-stones, placed, on the surface of the ice, and went 

 every evening and morning to observe the amount of the pro- 

 jections of the stakes. The observations were made without 

 interruption from the 12th to the 22d of July, and yielded 

 an ablation of 2 inches and 1 line per diem. The ablation 

 occurs chiefly during the day, and is most abundant on calm 

 days, as then the melting and the evaporation both act with 

 great intensity: it is less abundant during rainy days, and 

 is very inconsiderable, or does not take place at all on misty 

 days, or when the surface of the glacier is covered with snow* 

 Finally, it is not sensible during the night, except when it rains. 



This loss of substance is so great in quantity, that at first 

 sight we cannot but inquire, How does it happen, that, with 

 such an ablation, the glaciers can have so protracted a course % 

 for it is manifest that the diff*erence of thickness between the 

 origin and the termination of the glacier is not sufficient to ac- 

 count for the superficial loss. It must necessarily happen 

 then, that the glacier repairs the loss some way or other ; in 

 other words, that somehow or other it renews itself during its 

 progress. This renovation, or increase by intersusception, as 

 M. Elie de Beaumont calls it, is so imperatively required by 

 the actual state of matters, that the majority of authors have 

 admitted it, whatever the theory be by which they account 

 for it. 



The cause which produces this interior renovation can be 

 nothing else than the water which percolates into the interior 

 capillary fissures, and which, congealing in them, dilates the 

 mass of the glacier. The following comparison, though some- 

 what trivial, may perhaps facilitate the comprehension of this 

 important fact. Let us suppose, for an instant, that instead 

 of ice, the glacier were composed of a current of soft paste re- 

 posing on an inclined plain, and that every day there was intro- 

 duced into this paste some leaven to make it ferment. Let us, 

 moreover, suppose, that every day there was taken from this 



