166 The Problem of Flight : [February, 
snow or ice. Mansfield, in his work on ballooning, suggested 
that the weight of a man might be taken off by ballooning. 
A balloon of 18 feet diameter would take off the weight of a 
man ; and in this way a man named Ward was able to leap 
in the forest, from tree to tree, with a velocity of 15 miles 
an hour. In this case a man might guide a sledge of dogs 
at a great pace, and could convey stores by this means to 
any point. 
With regard to the nature of hydrogen gas in a severe 
frost, Mr. Reece said he had submitted the gas to intense 
cold, and it appeared to have no effect upon it. Faraday 
exposed it to cold ioo° below zero and a pressure of 800 at- 
mospheres, and never found that either had the slightest 
effect upon it ; neither had the most intense cold or pressure 
that he could produce at the Royal Institution. 
Mr. Simmons remarked that the hot-air balloon seemed to 
be the best adapted to the especial object — 
1. Because in the presence of intense cold, wind does not 
exist, wind being the chief drawback to the inflation 
of hot-air balloons in England. (Mr. Simmons’s ex- 
perience in this matter was confined to Canada ; he 
had not visited the ArcStic Regions.) 
2. Because the more intense the cold of the air surround- 
ing the balloon, the greater the ascending power. 
3. The hot-air balloon during inflation will give off suffi- 
cient heat from its surface to keep the men warm 
whilst they are holding the net, and when the balloon 
is afloat no inconvenience can be experienced from 
cold. 
4. The time required for the inflation of the hot-air bal- 
loon is about half-an-hour, and the preparation of the 
apparatus for the inflation will never be found so 
troublesome or occupy so much time as that for the 
hydrogen balloon. 
5. The danger and annoyance from carrying oil of vitriol 
will be obviated. 
6. Hot-air balloons have no preparation spread upon their 
surfaces that can sustain any injury, decomposition, 
or spontaneous combustion from being closely packed 
for a lengthened period. 
The entire weight of the balloon apparatus used at the 
Royal Arsenal, Woolwich, was 1200 lbs., its diameter was 
70 feet, and the heat when inflated, taken 10 feet above the 
open neck of the balloon, was 120° F. 
The greatest difficulty against the inflation of a balloon 
with pure hydrogen gas in intensely cold regions would, in 
