e 
wind, or any other wind, or a dead calm, or wind vertically down- ae 
| . Wards, or upwards, or at any other angle, are identical states y - 
x while the force will be that of gravity. The surface now has 
Weight. It isa body plus a force, and the entire matter is the 
: ane that we have been BERS ed The agit: is a E 
1886.] The Mechanics of Soaring. Sat 2: 
is the direct result of this force. While the lateral motion is 
going on at the rate of thirty feet per second, twelve pounds per 
second of air disturbance “is flowing past the edge å, while but 
three pounds is required to give the lateral thrust and furnish the 
two-pound rest. If this edge be rounded upwards along its sev 
enty-two inches of length to serve as a base for the expanding air 
to act against, it will give the needed three pounds and still leave 
nine pounds to go to waste by falling to the tension of the sur- 
rounding air. With this substitution the soaring action is com- 
plete. The force is now translating the body at right angles to 
its own direction: It will be noted that a velocity towards. æ 
greater than thirty feet per second will cause the surface to move 
contrary to the direction of the force faster than with it. Also, if 
a greater inclination be supposed, the abutting force would be 
greater, and the above contrary motion augmented. A limit 
would soon be reached in this direction; however. At an incline 
of one to four the rest would be three pounds, at one to three, 
four pounds, which latter would pass the limit of soaring, as it 
would require a rear expansion of five pounds to effect lateral 
motion, a utilization of five-twelfths of the entire force, which 
would surpass the ability of the system. 
A single further peculiarity is to be noted. Suppose the indefi- 
nite body of air belonging to this system to be in motion, either 
with, or against, or at any angle whatever to the direction of the © 
force. The action of the parts of the system would remain 
unaffected by such motion. It is universally recognized that the Ț 
translation of a system as a whole has no effect on the AE = 
tion of its parts. tag 
Let us now suppose the motion of the body of air containing 
the system be towards the earth’s atmosphere in a direction tan- _ 
gential to its surface, at the rate of one hundred miles per hour; 
until the air of the system and the atmosphere became identical, f 
we would have a bird soaring in wind of that velocity, and this 
z 
air so far as the soaring system is concerned. 
-In the earth’s atmosphere, surface and air will remain the 
