366 Account of a Journey to the 



to observe, as all the rest were covered by the ice and the 

 snow. I here discovered a repetition of those calcareous 

 banks interlarded with silex, which I saw at the Port de Pi- 

 nede. They afreet in the like manner a situation nearly ver- 

 tical, and a direction parallel to that of the chain ; they 

 are accompanied with laminae of another calcareous stone, 

 very much charged with sand, and which contain so great 

 a quantity of lenticular numismals, that they often seem to 

 be almost entirely formed of them. 



When we arrived at this terrace we were obliged to 

 ascend the glaciers, by the lower precipices of which I had 

 been hitherto stopped ; but this time I approached them at 

 their origin, and consequently at the place where they have 

 the least inclination. The passage, however, was disagree- 

 able and very dangerous : sometimes the surface was slip- 

 pery, hard, and resisted our cramp irons; sometimes we 

 sunk into the fresh snow, which had fallen on the summits 

 towards the middle of July. Beneath this snow we felt 

 fissures, where we were every moment in danger of being 

 lost. Other fissures were open, and opposed our passage ; 

 and we had very nearly been stopped by the last, at the di- 

 stance of two hundred yards below the summit. This fis- 

 sure extended transversally from the commencement of the 

 glacier as far as the precipices of the valley of Beousse. 

 We had no other resource than to clear this interval by 

 leaping down : we did so, and succeeded : this was the last 

 obstacle we had to encounter. I measured the visible 

 depth of this fissure, and found it to be 50 feet; and as 

 the point where we passed corresponded to the convexity 

 of the mountain, it was evident that it was the place where 

 the glacier had the least thickness. 



From this place I beheld the summit, which before had 

 been concealed from me by the disposition of the declivi- 

 ties which I had traversed. It appeared under the form of 

 an obtuse cone, covered with the purest snow. The sun 

 shone at the time in full splendour, and the sky appeared of 

 a dark blue colour, so strongly tinged with green that my 

 guides were struck with its strange appearance. The former 

 shade has been observed on all high mountains, but there is 

 no instance of the second ; and I do not know to what 

 cause this singular optical illusion is to be ascribed. 



At a quarter past eleven I reached the summit, and had 

 at length the pleasure of seeing the Pyrenees at my feet. I 

 immediately prepared my instruments for making expe- 

 riments. A violent wind prevailed at east-south-east, 

 which rendered this operation very difficult, and which occa-, 



eioned 



