1886] . Gravitation and the Soaring Birds. 519 
In going over, the one fifth that traveled -108° was wasted, 2. ¢., 
it neutralizes an equal amount of the other, so that only forty- 
eight pounds, instead of sixty pounds, are available to drive the 
plane edgeways; but this would be competent to produce an 
enormous velocity. Had the force been originally in cd, the 
entire sixty pounds would have been available. 
But when we rectify the diagram so as to make ef vertical, 
and add two pounds weight to the plane, so that the force em- 
ployed will be gravity, all the ghosts, which we supposed laid, at 
once reappear in vastly magnified proportions, The outcry now 
is, that the law of falling bodies is violated, for a body in falling 
can do no more work than sufficient to lift it through the same 
Perpendicular height. It seems that here is a good place to 
establish an €xception, and we will examine into the way in which 
it may be done. 
While the plane A B is level, the gravitating force is not re- 
Solved by it, but acts at right angles to the surfaces, when lateral 
Motion will be resisted by nothing but atmospheric friction, and a 
this the one or two pounds is competent to overcome, driving the 
plane to D while it is falling the thirty feet in which the sixty re 
Pounds is developed. It will therefore pass to H, the resultant of 
two motions. It will simply have a lateral motion of 150 feet 
Sways through the air added to its fall of thirty feet. To its 
Work of air compression there will be joined an additional item — 
x work in Overcoming 150 feet of atmospheric friction. The i 
