A Week a 
by De Saussure, for the deep 
considered as exaggerated—an opinion in which I should agree, if 
; but that there is one, and indeed 
s depth, below the Grand Plateau, I 
confidently affirm. 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, 
temaitting 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 alway ” 
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 
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