ON THE PROGRESS OF AERONAUTICS. 
367 
The fish, then, would fall to the bottom like a lump of 
platinum without the ability to rise. It is the bird without 
wings, for the same thing would happen to the bird, did it not 
possess the ability to convert the force of gravitation into hori- 
zontal force by the manipulation of its wing surface, for it 
thereby covers and controls the weight of air, which in a given 
time is included, and passed over, within the breadth of the 
wing-tips. If necessary, gravitation may be still further- 
diverted by the impact of the wing upon the air, because the 
resistance of the air bears a certain accelerated proportion to- 
the rapidity with which it is displaced. This fact, so important 
to the hopeful student of aeronautics, is simply illustrated by 
the alternately slow and rapid waving of any light plane sur- 
face, such as a fan. 
We have seen, then, that the fact of the specific gravity of 
the fish, and that of the element in which it disports itself, being- 
nearly the same, presents no encouragement to the employment 
of the balloon as a means of locomotion, but it does afford 
encouragement for the adoption of the only suggestion made in 
its favour by the Aeronautical Society, because the fish possesses 
the power, within a narrow limit, of making itself lighter or 
heavier, and this is just the quality which we desire for the- 
balloon, but to which, independently of throwing out ballast* 
or parting with gas which cannot be replenished, we have not 
yet attained. 
In this direction, therefore, lies the one improvement of 
which the balloon is capable, viz. the means to secure its ascent 
and descent without expenditure of gas or ballast. 
The power required to raise a mass which already possesses 
buoyancy is very slight compared with that which is requisite 
to propel against a resistant atmosphere. The effect also of 
the more simple power would be incomparably greater, because 
upon the supposition that a balloon required an additional 
power of 20lbs. beyond the gas with which it is inflated to raise 
it into the air, the application of a slight mechanical arrange- 
ment would clear it from all obstructions and bring it under 
the influence of another power, viz. the air in motion which 
would give it horizontal direction, and if that direction is not 
the one desired, it might raise it in search of another. The 
cessation of the mechanical action would also bring it down to 
the ground. Apply this power equal to 20 lbs. to a propeller 
working horizontally, and its inadequacy to effect any satisfac- 
tory result in a direct line becomes apparent. In comparison 
with the space to g be travelled, the rate at which propulsion 
could be attained would be utterly insignificant. 
Here let the imagination have a little play. For purposes of 
enjoyment it is not necessary to mount into the clouds. Our 
