hee” 
Sty 
% 
534 Editoxs’ Table. [June, 
would descend along the “rest” with the uniform velocity of 
30 
V(sin8 on per second, 
We are now prepared to answer the query proposed by 
Mr. Lancaster as a crucial test of the validity of his theory, viz., 
“Will the tilted surface, supplied with the rest of two pounds and 
moving with uniform velocity, obey the impulse of an external 
- force applied in its own plane with equal facility in any direc- 
tion ?” 
The above formula for uniform velocity of descent indicates 
that, for all inclinations of the plane, there is an unbalanced force 
which acts downward and parallel with the face of the plane, and 
therefore toward the “rest.” The tilted surface therefore will 
Or horizontally, solely by the action of that force.” 
nature were frequent and irresistible in the most ancient periods 
not “ obey the impulse of an external force applied in its own 
plane with equal facility in any direction.” 
“ The implication of the case” therefore is, that if an inclined 
plane is free to descend through the atmosphere, by virtue of its 
weight, it will, in consequence of the atmospheric resistance, move 
laterally downward unless it encounters a current of air that, be- 
ing resolved by the under surface of the plane, gives a vertical 
_ component which is equal to or greater than the weight of the 
plane, in which case the plane will move horizontally or ascend; 
or if the plane is properly shaped it may, in consequence of “ rear 
expansion” of the air, remain Stationary with respect to the 
ea 
It follows that all of the cbserved phenomena of soaring are in 
accord with the recognized principles of mechanics, but I trust it, 
-is sufficiently obvious, from the preceding discussion, that a soar- 
- 
ing bird is ot “ translated at right angles to the gravitating force, 
:0:— 
EDITORS’ TABLE. 
EDITORS: A. S. PACKARD AND E. D. COPE. 
‘ time, and they diminished in number and importance as life 
Me 
: 
i 
: 
4 
4 
a 
: 
