266 it*rofessor Agassiz on the Glacier Theory. 



assembled that same year at Porrentruy. I had myself, like- 

 wise, remarked this phenomenon on the Glacier des Bois, dur- 

 ing an excursion which I made at the same period, and after- 

 wards on the glacier of the Aar ; but it presented itself no- 

 where with that striking distinctness we witnessed last year ; 

 and it is on this account that, like several other facts which 

 continued observations could alone elucidate, it is only men- 

 tioned in a vague manner in my Etudes sur les Glaciers. 



During the months of August and September 1841, this 

 phenomenon was so well developed in the glacier of the Aar, 

 that it could not fail to strike every observer, especially in the 

 environs of the Hotel des Neucbatelois, at a height of 7500 feet, 

 and at a distance of two leagues from the extremity of the 

 glacier. I shall now endeavour to describe it, and to give an 

 account of the researches carried on with a view to ascertain 

 its extent and modifications. 



It is known that in general the ice of glaciers differs 

 from ordinary ice, by having a network of capillary fissures, 

 which seems to penetrate its whole mass, and is the result 

 of the transformation of the neve into ice. But this ice is, 

 nevertheless, of great compactness, and though rough at its 

 surface where it is not covered by a moraine, that appear- 

 ance is only superficial ; and it suffices to remove the external 

 crust, to find the ice as compact as under the moraine, and 

 at every place where it is sheltered from evaporation. If, 

 then, we examine this ice, we find that it is by no means uni- 

 form, but, on the contrary, that it is composed of laminae or 

 vertical bands of variable breadth, being generally from i to 1, 

 2, and 3 lines, but sometimes also from 1 to 2 and even from 4 

 to 5 inches broad. One set have a bluish tint, and a very com- 

 pact and homogeneous texture ; and the others have a white 

 colour, their ice being less hard, and having a snowy appear- 

 ance, in consequence of the quantity of bubbles of air with 

 which it abounds. The whole may be compared to a mass of 

 glass, composed alternately of dull bands with air-bubbles, and 

 bands which are perfectly transparent. This particular ar- 

 rangement of blue bands alternating with white ones, is par- 

 ticularly apparent in the walls of the crevasses. The bands pass 



