This paper is intended in the first place to ascertain some definite and tangible ideas as to dimensions of the vital parts of machines “ heavier than air” designed for aërial navigation. The vital parts are, of course, the engine and propeller.

In the second place it is proposed to discuss the aëroplane and its functions in an airship.

In all engineering problems the first requisite towards a solution is to reduce things to numerical values. An inventor may imagine a design for a machine, but he cannot put it into practice without calculating out the necessary dimensions, and such, calculations, when undertaken, often either confirm or condemn the design.

Much of the experimenting at present going on is evidently entered upon, and carried on, without any calculations at all, the only results being a waste of time and money.