Aérial aii 25 
tion of weight to either, or percussion will give it the ascendency. 
An aérial machine, whose gravitating and ascensive powers are equal, 
whatever be its size, shape and weight, will, by weight or percussion, 
move upwards or downwards, as the one or the other of these pow- 
ers has the ascendency. ‘Therefore its ascent or descent can be ea- 
sily managed, so as to insure ascent by percussion, and sit a4 
its gravity, the wings being stopped. 
On these principles, an aérial machine of any size, by balancing, or 
nearly so, its ascensive and gravitating powers, can be made so as to 
carry any required weight, and it can be governed by percussion ; 
being once well constructed, it would remain a ready vehicle fitted 
to move equally in every direction, and there would be no need of a 
valve to discharge the included air, to enable it to descend, or if there 
were, it would be used only in case of necessity. The ascensive 
powers of aérial fluids, lighter than common air, have already been 
determined, and 1 have made and hung wings on the aforedescribed 
principles, and found their motion very easy and their percussion ve- 
_ ty powerful; therefore the practicability, of aérial navigation, can- 
not be reasonably doubted. The navigation of the air will be at- 
tended with nearly the same advantages and disadvantages as that of 
water. The aéronaut, during a storm, is however, Jess liable to dan- 
ger than the seamany as he has the power of descrying it at a great- 
er dist asce t at pleasure ; he can rise above 
the danger or descend atid ‘anchor fast, or as the wind | 
moves from or before it, he can take its current, which will bear 
him from danger, if he keeps sufficiently elevated, while the seaman 
has no alternative, but either to anchor fast, or if that be impossible, 
to weather all vicissitudes and dangers. If the aéronaut wishes to 
move in an opposite direction to the wind, he must rise, (as the at- 
mosphere is composed of different strata of air, moving at different 
altitudes, in different directions,) till he finds a favorable current, or 
wait till the wind in the lower strata blows right, or until it is calm. 
To what altitude it is possible to ascend on these principles, will de- 
pend on the balance between the density of the air and the powers 
of gravity ; for it is evident, that the gravity is directly as the densi- 
ty. Conveyance by air can be easily rendered as safe as by water or 
Jand, and more cheap and speedy, while the universal and uniform 
diffusion of the air over every portion of the earth, will render aérial 
navigation preferable to any other. To carry it into effect, ‘there 
needs only an immediate appeal —— large scale, to ex- 
Vou. XXV.—No. 1 ° 
