1886. ] The Mechanics of Soaring. 327 
applied to the body in such a way as to move it at right angles 
to the direction in which the force acts. This translation of the 
body is “soaring.” It rests on two universally recognized laws. 
The most important is the conservation of energy, of which it is 
the most beautiful illustration to be found in mechanics. The 
other is the reaction in all directions of fluids under the action of 
mechanical forces. 
_ The body must be so constructed as to have at least two direc- 
tions of motion which are unequally resisted by the air. , 
The case will be first presented as operating in space devoid 
of gravitation, where the body will have no weight, and . 
afterwards the system will be introduced. into the earth’s atmos- 
phere. Implications arising from the action of gravity, and the 
constant tendency to introduce the earth into the soaring system, 
will be avoided Í 
Suppose the body to be an oblong flat surface, such as a sheet 
of tin 12 x 72 inches, and that æ 4 is its transverse section, and 
that the force moves from c towards d, at right angles to the sides 
* of the surface. 
é i č 
Se Ee P eee A, 
m S x 
5 
z : n ; d eo 
Surface at right angles to the direc- Surface inclined to the direction of 
tion of the force. the force. 2 
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