368 
POPULAR SCIENCE REVIEW. 
•aerial yacht requires but to skim the trees and buildings. Wafted 
across the wide expanse, it may skim the fields and rise to the 
hedges. With an envelope more impervious to the escape of gas, 
the voyage may be prolonged. Floating day after day, at the 
caprice of the wind certainly, but always over fresh scenery, 
nothing could be more enjoyable. 
During these excursions it would be possible to renew the 
gas by proximity to some gas works, and not seldom it might 
happen that, by waiting for it at anchor, a favourable wind 
might influence a return journey. It may here be remarked 
that any mechanical means such as a screw acting vertically in 
the car of a balloon, capable of exerting a force of thirty-five 
pounds, would save one thousand cubic feet of gas. 
It was intended by the society which I represent to try the 
effect of the screw acting vertically upon a balloon, but in the 
meantime the War Office authorities were induced to give a 
trial to the inventor of a screw by which he hoped effectually to 
propel the balloon. He was induced to attach also an arrange- 
ment which acted vertically. The following is an extract from 
Captain C. Orde Browne’s article, published in the 46 Popular 
Science Beview” for October 1874. 
44 The difficulty of ascertaining exactly when a captive balloon 
is balanced, when even a slight wind is blowing, so as to 
stretch the retaining rope, made the first trial a little doubtful ; 
and after one ascent, apparently due to the working of the 
propeller, a doubt arose as to the exact balance of the balloon, 
which might have a tendency to rise, and only have been held 
down by the captive line, which, except at very still moments, 
was pulled taut by the wind acting on the balloon. It being 
ascertained at a still interval that the balance was good, the 
vertical gear was worked, and the balloon again rose. The rate 
of ascent was difficult to estimate ; it was judged, however, not 
to exceed fifty feet a minute. A positive indication of the 
power of the propeller was thus obtained, and it should be 
noticed that the circumstances — if the rate of ascent only was 
measured — were rather disadvantageous, for the weight of the 
line up to the extent of forty feet was gradually added to the 
balloon as it rose. Had the mean rate of ascent and descent 
been taken, this error would be eliminated, for the descent would 
be favoured by the weight of the rope from forty feet in length 
at the maximum height, down to nothing at the ground.” 
The balloon was now liberated, and the report goes on to say : 
44 The horizontal gear, however, throughout the entire voyage 
failed to give any satisfactory results ; even allowing that the 
effect was perceptible, it is impossible to lay much stress upon it„ 
Any force would give a perceptible effect if recorded with 
sufficient delicacy. There is no use in an insignificant effect 
