Report of the Researches of M. Agassiz, 175 



Aar, and continued at a later period by M. Agassiz, are in 

 fact the whole of the materials of this kind which we pos- 

 sessed. It remained, therefore, not only that we should con- 

 tinue these annual measurements, but, that they might be 

 invested with a real value, it was necessary they should be 

 multiplied in numerous places. Daily observations were ne- 

 cessary to appreciate the diversity of the movement in hot or 

 humid days, and during cold ones ; and it required that these 

 observations should be repeated many times every day, that 

 the difference between the diurnal and nocturnal movement 

 might be brought out. Finally, that we might ascertain the 

 movement from one season to another, it was indispensable to 

 determine trigonometrically numerous points over the whole 

 extent of the glacier, which might be measured at all seasons 

 of the year. In a word, it became necessary to prepare a 

 chart of the whole glacier. 



With this question of the motion of the glacier, is con- 

 nected the one respecting the changes which the sarface of 

 the glacier undergoes. It is evident, that if the loss of sub- 

 stance which the glacier undergoes is compensated only by 

 the advancement of the superior masses, there ought to be a 

 certain relation between the superficial waste and the progres- 

 sion. But before we can arrive at precise results on this head, 

 we must also make a series of observations in different posi- 

 tions where the respective levellings are accurately taken, 

 and that these observations must be continued for a certain 

 time, so that the influence of external agents may be fully 

 appreciated. 



But in what way soever a glacier may move, it is a neces- 

 sary condition of this movement that it shall free itself from the 

 surface upon which it rests. This, at first view, at all events, 

 appears a condition imperatively required ; although there 

 seem to be facts which go to prove that the glacier is frozen at 

 its lower surface, and MM. Agassiz and de Charpentier are 

 disposed to admit there may be a slow movement, even sup- 

 posing that the lower surface of the ice was frozen to the 

 part beneath. However this may be, this theory requires to 

 be supported upon additional observations before it can be 



