A Week among the Glaciers. 285 



by De Saussure, for the deepest, at six hundred feet, which has been 

 considered as exaggerated — an opinion in which I should agree, if 

 this depth is given as common ; but that there is one, and indeed 

 that there are several, of this depth, below the Grand Plateau, I 

 confidently affirm. One in particular, which I measured with a 

 rude instrument constructed on the spot for the purpose, proved to 

 be between eight and nine hundred feet deep ; it was but a short 

 distance from the Grand Mulets. This crevasse, as I should judge, 

 was about one fourth of a mile in width, and seemed to have been 

 formed by the inferior side sliding down to the distance mention- 

 ed above as the width of the crevasse, while its superior portion, 

 remaining apparently stationary, (I say apparently, because the 

 whole mass is perpetually moving onward,) had increased in 

 height, by the additions made to it from the falling avalanches, 

 so that the upper side rose more than two hundred feet above 

 the inferior border of the crevasse ; consequently, measuring its 

 depth from the highest point of its upper edge, it measured near 

 nine hundred feet, while from the highest point of its inferior 

 border, my instrument marked something less than six hundred 

 feet. This I give as the maximum of depth of any crevasse 

 which we observed in this ascent. The crevasses are however, 

 generally, from a few feet to fifty or sixty deep. Many have their 

 sides nearly perpendicular, but in the deeper ones they are always 

 zigzag, and many of the deepest, when they are very wide, may 

 be descended with but little risk by means of ropes and hatchets, 

 which are a necessary accompaniment to these expeditions. The 

 crevasses which are the most difficult and dangerous to cross, are 

 those whose width is about sixty or eighty feet, and eighty or 

 one hundred deep. These frequently extend to a great length, 

 and to avoid the fatigue attendant on following them parallel to 

 their length, an attempt is sometimes made to pass on the bridges, 

 which have been formed by avalanches falling across them, and 

 thus wedging in immense blocks, forming in many places a rude 

 but substantial arch, which rises some ten or twenty feet above 

 their borders, and as many wide, making a very safe and conve- 

 nient passage, while others at their base are sufficiently wide to 

 tread on with perfect ease and safety. At the apex of the arch, 

 they become so narrow, by melting, that it is quite impossible to 

 stand erect upon their summit ; it being only a few inches wide, 

 and sloped on either side like a saddle, one is obliged for a few 



