ortunately neglected to mark the
time at which they were made--a point of material importance, for the
results would of course be modified by the progress of the day; and it
would have added to their value, had these observations been compared
with similar ones made at the same time at the observatory. During the
ascent of the balloon, the hygrometer was variable, but obviously marked
an increase of dryness; the thermometer indicated a decrease in the heat
of the atmosphere, but the decrease is not uniform, the ratio being
higher in the elevated regions than in the lower, which are heated from
the earth; and it was found, by not fewer than fifteen trials at
different altitudes, that the oscillations of a finely-suspended needle
varied very little from its oscillations on the surface of the earth. At
the height of 21,460 feet. Lussac admitted the air into one of his
exhausted flasks, and at the height of 21,790 feet, he filled the other.
He continued to rise, till he was 22,912 feet above Paris, or 23,040
feet--that is upward of four miles and a quarter--above the level of the
sea, the utmost limit of his ascent, an elevation not much below the
summit of Nevado de Sorato, the highest mountain of America, and the
loftiest peak of the Himalaya in Asia, the highest mountains in the
world, and far above that to which any mortal had ever soared before.
One can not but admire the intrepid coolness with which Lussac performed
his experiments at this enormous elevation, conducting his operations
with the same composure and precision as if he had been seated in his
own parlor in Paris. Though warmly clad, he now began to suffer from the
excessive cold, his pulse was quickened, he was oppressed by difficulty
in breathing, and his throat became parched, from inhaling the dry,
attenuated air--for the air was now more than twice as thin as ordinary,
the barometer having sunk to 12.95 inches--so that he could hardly
swallow a morsel of bread. He alighted safely, at a quarter before four
o'clock afternoon, near the hamlet of St. Gourgan, about sixteen miles
from Rouen. On reaching Paris, he hastened to the laboratory of the
Polytechnic School, to analyze the air he had brought down in his flasks
from the higher regions; and, by a very delicate analysis, it was found
to contain exactly the same proportions as the air on the surface of the
earth, every 1000 parts holding 215 of oxygen, confirming the identity
of the atmosphere in all situa