imple experiments now embarked upon showed the behaviour
of magnetised iron, as also of a galvanic pile or battery, to remain
unaltered. As their altitude increased their pulses quickened, though
beyond feeling keenly the contrast of a colder air and of scorching rays
of the sun they experienced no physical discomfort. At 11,000 feet a
linnet which they liberated fell to the earth almost helplessly, while a
pigeon with difficulty maintained an irregular and precipitate flight.
A carefully compiled record was made of variations of temperature and
humidity, and they succeeded in determining that the upper air was
charged with negative electricity. In all this these two accomplished
physicists may be said to have carried out a brilliant achievement, even
though their actual results may seem somewhat meagre. They not only
were their own aeronauts, but succeeded in arranging and carrying out
continuous and systematic observations throughout the period of their
remaining in the sky.

This voyage was regarded as such a pronounced success that three weeks
later, in mid-September, Gay Lussac was induced to ascend again, this
time alone, and under circumstances that should enable him to reach an
exceptionally high altitude. Experience had taught the advisability of
certain modifications in his equipment. A magnet was ingeniously slung
with a view of testing its oscillation even in spite of accidental
gyrations in the balloon. Thermometers and hygrometers were carefully
sheltered from the direct action of the sun, and exhausted flasks were
supplied with the object of bringing down samples of upper air for
subsequent analysis.

Again it was an early morning ascent, with a barometer on the ground
standing at 30.6 inches, and a slightly misty air. Lussac appears
to have accomplished the exceedingly difficult task of counting the
oscillations of his magnet with satisfaction to himself. At 10,000 feet
twenty vibrations occupied 83 seconds, as compared with 84.33 seconds at
the earth's surface. The variation of the compass remained unaltered,
as also the behaviour of magnetised iron at all altitudes. Keeping his
balloon under perfect control, and maintaining a uniform and steady
ascent, he at the same time succeeded in compiling an accurate table of
readings recording atmospheric pressure, temperature and humidity,
and it is interesting to find that he was confronted with an apparent
anomaly which will commonly present itself to the ae