The Sun.
London, England, 1866-06-26 00:00:00

TO TILE EDITOR OF THE SUN.

SIR,—As one of the council of the Aeronautical
Society of Great Britain I know how much aeros-
tation at the present time is becoming more and
more a subject of interest ; I therefore venture to
give an account of an ascent that took place at
Widsor, on Saturday, June 9, conducted entirely] by
two amateurs, and, to the best of my knowlege,
one of the first that has taken place for very many
years, with the exception of the scientific ascent
made by Mr. Glaisher, F.R.S., and myself a week
or two ago.
On Saturday last it was arranged that Mr. Glaisher
and myself should make another scientific ascent,
but through unforeseen circumstances that gentle-
man was unable to accompany me, so I arranged to
take Mr. Burnaby, one of my brother officers.

At 5 20 p.m., the balloon being fully inflated and
ready, under the superintendence of my aeronaut,
Mr. Hampton, Mr. Burnaby and myself took our
seats in the car and left the ground. We rose but
slowly, according to my wish, and the wind, which
was blowing in a N.N.E. direction at the rate of
about 10 or 12 miles per hour, bore us gently over
the river towards Eton. It is here worth while re-
marking that, while passing over the bright surface
of the river, the diminution of radiation was so much
that the upward course of the balloon was immedi-
ately checked, and the gas sufficiently condensed to
cause her to descend. A small portion of ballast
soon gave us an upward turn. We sailed right up
the High-street of Eton, over the chapel, the school
yard, and the playing fields, where I had but a few
years ago enjoyed many a game of cricket, and now
saw a match going on.
We were now 500 ft. from the ground, and slowly
rising.
At 700 ft., just having left the playing fields about
100 yards, we let out a parachute from our car on
Garnariu's principle, which at first descended very
slowly and smoothly, but before it reached the ground
(which was not until it had passed at least 500 yards
over the :railway to the west of Slough Station) it
began to oscillate very violently. Not having Mr.
Glaisher with me to make observations at high alti-
tudes it was my object this evening to try expe-
riments with the balloon near the earth, which might
be useful when economy of gas and ballast is required
for a long voyage, e.g., noticing the various causes
of expansion and condensation of gas when passing
over water, a valley, a hill, changing currents, the
sun's rays, or their direct interception by a cloud
and its density, a shower of rain, and various other
causes.

The river at Eton gave me a very good example
of the condensation by water, as the density of the
clouds at starting being the same when passing over
the river could not be the cause. When passing
over a valley I noticed each time that we rose the
gas expanded, and the reverse effect when passing
over a hill ; showing that the concave surface con-
centrated the rays of radiation on us, while the con-
vex dispersed them, the flat being the medium. We
passed through various currents of air at the same
altitude, which also caused a certain amount of con-
densation and expansion. Clouds of different den-
sity, and the direct sun's rays coming on the balloon,
I also watched their effect ; but the most striking
and ostensible effect of all was the immense degree
of condensation caused by a slight shower of rain
falling on the balloon, which caused her to descend
so rapidly that, had we not been over 2,000 feet
high, it would have been almost impossible to com-
pensate for the condensation by the throwing out of
ballast before we should have reached the ground.
This was caused not so much by the weight of
water that fell on the balloon, as by the cold pro-
duced by the evaporation after it had fallen all over
the surface of the balloon.
There is another fact which I noticed, viz., that
the rotatory motion of the balloon is caused in a
measure by the netting acting as a screw through the
air in the ascent and descent of a balloon, so
that, if the netting can be so placed that the cordage
comes
ry
the equator at right angles,
I fi
circular motion could be so
straight,
beeNre cutting
that
much controlled that the car of a balloon might be
used for photography. It was for these objects that
I kept the balloon (as near as could be) at the same
altitude, and especially to expend as little ballast as
possible to prolong the trip.
These observations, though they may seem of
little importance generally, are very necessary when
a balloon is required to be quietly managed for
scientific observations.
The highest we rose was 3,000 feet, and the result
of the trip was much the same in its details as others.
We passed over a lovely country and magnificent
mansions between Eton, Slough, and Great Berk-
hamptead. Then passing successively over the vil-
lages iind country between Dunstable and Ampthill