ago. ‘The Mechanics of Soaring. [April, 
velocity in the plane of the surface. It is two pounds at all 
velocities; motion in the plane of the surface does not change the 
| value of the condensations, but only their character. It makes 
i them thinner but wider, the total of twelve pounds being constant 
~ atall velocities; so that the two-pound abutment can only vary 
with the inclination of the surface to the direction of the force. 
It is obvious that a force applied to the surface in the direction of 
its length, will move it either way indifferently. It can be seen 
at once that the two-pound rest will not resist such a force at any 
velocity whatever in these directions. Leaving unnoticed any 
oblique motion neither longitudinal nor transverse, the important 
point is, will a given force, say of one pound, move the surface 
towards a, with the same velocity as towards 0 ? 
ee It is possible that when the lateral motion is set up there might 
be developed in the air disturbances, differences which woul 
require an increase or diminution of velocity towards 4, to. bal- 
ance the twelve pounds, and that these differences would be 
-.. greater or less towards 6 than a, But this would in no way affect 
a the lateral motion; Acceleration or retardation would go on 
until equilibrium again occurred, so that it would bea balanced 
surface which is moved. The vital point is: Does or can the 
twelve pounds in any way resist the lateral motion either towards 
: aorġ? It seems evident that there is no conceivable way 
=, , which the lateral motion in either of these directions can be 
: resisted by the twelve-pound force, under these conditions, with- 
‘out at once traversing the law of the conservation of energy. 
- — The only resistance to be found is the skin friction on six square 
_ feet of smooth surface under a pressure of two pounds to the 
Sey foot. ` 
= Tf this be a fact the case is proven. There is no other feature 
-of it which would be denied. | 
-Note the implications of the case. The lateral motion caused ; 
_ by the one pound would now carry the surface to 4, while it 15 
inches with that direction, so that its path is at right angles to it. 
