DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.70267#0457
BALLOON INTELLIGENCE IMPROVED. 411
fourteen inches in the focus of a lens, lose one third of
their intensity, and when refracted by the prism, no longer
exhibited lively and distinct, but weak and confused co-
lours. Weights attached to a spring balance lost one half
of their gravity. The magnetic virtue he found decreased
as the square of the distances; but at the elevation in
question, the needle began again to put itself in motion.
When about seven thousand two hundred feet from the
earth, he enclosed in an instrument by M. Hez, four
inches of the surrounding air along with mercury, and
marked exactly the point where the air and mercury were
united; and when he returned to the earth, he found that
The mercury filled the whole tube within a tenth.
M. Robertson passed between two large clouds, which
seemed to afford a passage to the balloon; the form of
these masses of vapour was oblong, and they resembled
rags suspended above the earth. Their uppermost parts
did not form in their aggregate a smooth surface, as ap-
peared to those who viewed them from the earth, but re-
sembled long pyramids, occasioned probably by caloric
raising the mass in proportion to the density of the at-
mosphere ; they appeared to plunge towards the earth, in
consequence of an optic effect, resulting from the ap-
parent immobility of the balloon, which, however, was
at the time rising at the rate of fifty feet per second.
When the thermometer indicated one degree above
freezing, and the barometer stood at fifteen inches, M’«
Robertson set two pigeons at liberty, and they descended
with the rapidity of lightning in a plane, slightly inclined,
without moving their wings. When the barometer stood
at fourteen inches, he let off another; but after flutter-
ing with difficulty for a moment, it perched on the net-
work, and would not quit it. Two butterflies, let go at
the same time, tried to use their wings, but in vain.
M. Robertson is preparing a balloon of between
forty
fourteen inches in the focus of a lens, lose one third of
their intensity, and when refracted by the prism, no longer
exhibited lively and distinct, but weak and confused co-
lours. Weights attached to a spring balance lost one half
of their gravity. The magnetic virtue he found decreased
as the square of the distances; but at the elevation in
question, the needle began again to put itself in motion.
When about seven thousand two hundred feet from the
earth, he enclosed in an instrument by M. Hez, four
inches of the surrounding air along with mercury, and
marked exactly the point where the air and mercury were
united; and when he returned to the earth, he found that
The mercury filled the whole tube within a tenth.
M. Robertson passed between two large clouds, which
seemed to afford a passage to the balloon; the form of
these masses of vapour was oblong, and they resembled
rags suspended above the earth. Their uppermost parts
did not form in their aggregate a smooth surface, as ap-
peared to those who viewed them from the earth, but re-
sembled long pyramids, occasioned probably by caloric
raising the mass in proportion to the density of the at-
mosphere ; they appeared to plunge towards the earth, in
consequence of an optic effect, resulting from the ap-
parent immobility of the balloon, which, however, was
at the time rising at the rate of fifty feet per second.
When the thermometer indicated one degree above
freezing, and the barometer stood at fifteen inches, M’«
Robertson set two pigeons at liberty, and they descended
with the rapidity of lightning in a plane, slightly inclined,
without moving their wings. When the barometer stood
at fourteen inches, he let off another; but after flutter-
ing with difficulty for a moment, it perched on the net-
work, and would not quit it. Two butterflies, let go at
the same time, tried to use their wings, but in vain.
M. Robertson is preparing a balloon of between
forty