On Aérial Navigation. 325 
at a pound per yard; hence the weight would be 5750 pounds, 
Let the car, chimney, &c. be taken at 2000, and there would be 
the power of 3050 left unoccupied, inaddition to the power of 6,800 
pounds for effecting its progressive motion : however, it would 
be necessary for one hour’s travelling to carry about 2000 pounds 
weight of fuel, which would only leave power to convey a crew 
of seyen men: hence it would be more suitable to carry about 
20 men, and to reduce the ascending velocity to 15 miles per 
hour, allowing the descent to remain at the full speed, which 
would reduce the general speed to 174 miles per hour. 
This statement plainly shows that the Montgolfier balloon | 
have described is the least that would be efficient, which | trust 
will shield me from the imputation of holding extravagant opi- 
nions upon this subject in proposing it. Indeed the unwieldy 
bulk of these bodies is unwillingly thrust upon me by the result 
of calculations grounded upon the facts of the case. 
The danger attending the hydrogen gas balloon, where any 
first mover is used that acts by fire, is a great obstacle to their 
introduction ; otherwise a balloon of this kind equal in power 
to the one described, would not exceed 70 yards in length, and 
would meet with rather less than half the resistance, and. of 
course not consume more than half the power to drive it at the 
proposed velocity—there are other inconveniencies attending 
these balloons, and their cost in filling is not one of the least. 
The great resistance upon the prow must be balanced either by 
a firm wanded texture, or by internal condensation ; the former 
is heavy and incapable of being folded up, and the latter waste- 
ful, as it is impracticable to have it air-tight enough not to al- 
low a vast escapage. This would oblige a double structure, one 
of thin oiled silk containing the gas, and one of a coarser texture 
surrounding it, which could receive the condensation necessary 
from common air driven in occasionally by a pump; or perhaps, 
with some little contrivance an aperture at the point of the 
prow, receiving the full direct resistance of the external air, 
commensurate with the velocity of the balloon, would answer this 
purpose. The danger from fire might be greatly reduced by 
having the balloon at a considerable distance above the car, say 
20 yards, and the surface for waftage might be so arranged as 
to permit of a safe descent evén in the event of the balloon 
taking fire, and being obliged to be cut away. 
It was my intention to have ascertained what proportion of 
azote with hydrogen gas would render it incomlmstible on its 
access to common air; but owing to an acciddent in the experi- 
ment immediately previous to my leaving home, this must be 
reserved to a future opportunity ;—perhaps the adulteration re- 
quired may be so great as to render the specific gravity of the 
X3 mixture 
