bird. It is an inert body translated at right angles to the gravi- 
tating force, or horizontally, and solely by the action of that force. 
It has constant motion in the direction of gravity but does not 
lose its energy of position by getting nearer the earth. It resem- 
bles zx this respect a clock moved by a weight, and placed on the 
platform of an elevator which slowly ascends, While the clock 
weight is a falling body having motion in the direction of gravity, 
it still does not lose its energy of position by getting nearer the 
_' earth, because of another motion in which it is elevated. 
The surface, under the action of this force as above condi- 
tioned, is a splendid atmospheric highway maker. It lays down 
an endless cushion of air on which it travels with incredible 
speed. It is paralleled by nothing in nature. It is gravity in the 
role of a continuous motive power. It obeys implicitly the laws. 
of mechanics in every paroma and gives man complete domin- 
ion of the air. 
When the attention is directed to soaring in the earth’s atmos- 
phere, as exhibited by the birds, two delusions must be industri- 
ously guarded against. One is that wind is concerned in the 
phenomenon. The other is that the horizontal motion of flight 
is the result of a single impulse acting in one direction. 
_. When it is seen that motion is derived from gravitating force 
exhibited by the quiescent bird in all cases, and that its level 
flight is a compound result of two motions, one vertically down- 
wards, and one slanting upwards in the plane of the wing sur- 
faces, both simultaneously occurring, the subject assumes a more 
explicable form. 
- * Then when it is seen that no en is lifted in the upward 
ae slant, | this action bearing no resemblance to a ball rolled up an 
2 -inclined plane, the case will be in a fair way to be completely 
_ comprehended. 
In conclusion, I may be pardoned for indicating the direction 
a in which criticism of this paper may be fruitful. 
uN ae easy to lose oneself i in the limbo ofa vicious terminology: 
2 weaken the’ case. It will merely show an improper use of w 
_ Statements of fact regarding the plane inclined to the force, 
and Stee in the hossbility. of equal ease of motion in 
= $32 on The Mechanics of Soaring. [ April, 
= 
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