Summit of Mount Blanc. 9 
observations. Our ascent to the summit of Mount Blanc, 
then, may be considered a journey of curiosity: but it was 
our wish to examine the temperature and rarefaction of the 
atmosphere, to obtain an exact knowledge of glaciers and 
of the frozen region, and to survey the rocks. Our thermom- 
eter was broken the second day, when after taking the tempera- 
ture at the top, we were about to notice it at stated distances 
on our descent. Our vessels of air from the summit were 
injured in sliding down the declivities or in wading through 
the snow.—As to the rocks little can be said of them: the 
nature of the mountain has long been well known, and it 
would be useless to enlarge upon the accounts already given. 
Thus our journey has been of no avail in adding to our 
knowledge of the rarefaction of air at the top, yet we are 
satisfied with having made the attempt. It may be ascer- 
tained by a barometer, which we had not, or by fillmg many 
vessels, so that some at least might be brought down safe.— 
This too would allow a portion for analysis—I know not 
that the attempt has been made. 
Mons. de Saussure found the absolute height of Mount 
Blanc to be 14,700 feet: Delue made it 14,346: Prof. 
Pictet says it is 14,556 : while M. Tralles, who has measur- 
ed it three times, with the same result makes it 14,793 feet : 
making its absolute height 5,355 feet less than that of Chim- 
borazo ; but its relative height is greater, as it rises 11,532 
feet above the vale of Chamouny, while Chimborazo is ele- 
vated only 11,232 feet above the valley of 'Tapia—making 
a difference of 300 feet relative height. 
It was in 1760 that M. de Saussure seems first to have 
thought of measuring Mount Blanc, and offered a reward to 
the person who should discover a way to the summit. His 
offers were sufficient to induce many to make the attempt— 
and for twenty-five years, unsuccessfully. ‘The most impor- 
tant trials are recorded as follows. , 
The first attempt was made in 1762 by an inhabitant of 
Chamouny ; he failed as he only reached the glacier Bossons. 
In 1775 four men, following the same route, advanced to 
the mount de la Cole, running parallel to the glacier Bossons. 
In 1783 three others tried the same path, but were forced 
to return by a strong desire to sleep, which would have been 
fatal, if indulged. 
Vou. L.....Ne. 1. 2 
