In the following remarks I shall endeavour to point out the principles underlying the art of mechanical flight, and by a plain statement of the facts, hope to clear away the mystery which to a great many minds seems to surround the subject, and thereby induce engineers to give serious attention to the matter.

In order to sustain weight in the atmosphere, it is absolutely necessary to deliver air downwards, and in order to ascertain the weight of air acted upon, and the speed with which it must be moved, the following formula, so well known to marine engineers, is perfectly applicable where W is the weight of the mass of fluid acted upon in lbs. per sec, and S is the downward velocity in ft. per sec,G is 32.2ft. per sec.