Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/251

Rh individual systems of flow fuse into one greater system, and are not, as Langley supposed, independent, consequently they will each and all react on one another, and the more numerous they become the wider they will require to be separated.

A limiting width will evidently be approached asymptotically when the number of planes becomes very great, and the limiting condition is that which most nearly resembles that of our hypothesis, for the whole depth of the fluid is then acted on with approximate uniformity, and the sweep of each plane will be fairly represented by the area included between any two adjacent planes. Hence the value of $$k$$ deduced from experiments with pairs of superposed planes may he less than its true value according to the requirements of hypothesis.

§ 162. The Ballasted Aeroplane.—It has long been known that an aeroplane suitably ballasted will exhibit a certain degree of stability, and may be regarded in fact as a rudimentary aerodrome. This fact is mentioned by Mouillard in his "Empire de l'Air" (1881), who, however, bases his discussion on a quite fantastic theory involving a supposed change in the position of the centre of gravity due to changes of velocity.