t they refused to
proceed. The portion of atmosphere above us was entirely free from the
vapours which the lower strata always contain, and was truly the 'pure
empyreal,' seldom seen by mortal eyes. We had all our life beheld the
sun through a mist, but we now saw him, face to face, in all his
splendour. The guides asserted that the stars can be seen, in full
day, by a person placed in the shade. It being near noon, and the sun
almost over our heads, we could not find shadow to enable us to make
the experiment.

The air on the top of Mont Blanc is of but little more than half the
density of that at the surface of the ocean. According to the
observations of Saussure, the height of the barometer on the summit,
was sixteen and a half inches, while that of a corresponding one at
Geneva, was twenty-eight inches. In consequence of this rarity of the
air, a pistol, heavily charged, which we fired several times, made
scarcely more noise than the crack of a postillion's whip.

We remained an hour and a quarter on the summit, part of which time
was spent in useless regrets at not having waited to provide ourselves
with instruments, as we were now so admirably situated to make with
them a series of interesting experiments. Those which had suggested
themselves, were principally concerning the absorption and radiation
of caloric, and on the degree of cold produced by the evaporation of
aether and other liquids. We found the descent more easy and much less
fatiguing, though perhaps more dangerous than the ascent, on account
of the greater risk of slipping. We passed under the place where the
avalanche threatened us, with even more caution and more rapidity than
before, as we found that a small piece had actually fallen, and
covered our path since we had passed by. We arrived in about an hour
at the 'Grand Plateau,' where we stopped to refresh ourselves, and
gratify our returning appetites. We found the guide whom we had left,
quite relieved. Here the sun, reflected from the walls of snow which
surrounded us on three sides, poured down upon us with the most
burning heat that I ever experienced from its rays, while our feet,
cold from being immersed in the snow, prevented perspiration, and thus
increased its power. Wherever its rays could penetrate, as between the
cap and neckcloth, or even to the hands, it resembled the application
of a heated iron. We were compelled, in addition to the assistance of
our veils, to keep our eyes half