During the past year considerable advance has been made on the question of Aeronautics relating to flying arrangements heavier than air (exclusive of balloons). I have always maintained that the power required for bird life has been much over-estimated. Take, for example, the flight of the pelican, which I have often witnessed. A dead bird weighed 21 lbs., with an extent of wings of 10 feet from end to end, speed 70 strokes per minute, each stroke averaging about one foot. It is evident that during a period of gliding flight with motionless wings these sustain the whole weight of the bird. The exertion or force will be during the oscilating or downstroke of the wing against this pressure.

This machine was taken in hand in 1899 with the assistance of Mr. P. Y. Alexander. A staff of competent draughtsmen were employed in getting out fully detailed working drawings of different powers. The propellers are 30 feet in diameter revolving in opposite directions mounted on, separate shafts, one inside the other, by this means the necessary reactions for rotation is obtained. The steam engines are below; the engines in this particular design are of somewhat novel type; the bed plate cylinders are connected to one of the shafts, the outer one, and the crank shafts to the inner one, so that we have the engine bed cylinders, etc., revolving in one direction, and the crank shaft in the opposite direction.

The 30-foot diameter air propeller was mounted on a horizontal shaft. The propeller was of the double kind built up of solid drawn steel tubes tied and strutted together. The propeller was designed to give a thrust or lifting power of 600 lbs., and having a factor of safety of 3½, it weighed 120 without the canvas, the idea of the double form or superimposed structure was for reasons of strength.

It is on the same principle as a lattice or “ warren ” girder supported at one end and loaded at the other, the members of one blade being in compression and the other in tension.

This propeller was tested, and it gave way with 600 lbs. on the extreme top or 1,200 in propeller, a deflection curve was taken which showed that even with 600 at the top it was well within the limits of elasticity.

From the very beginning of aëronautics difficulty was experienced in obtaining an envelope sufficiently impervious to gas to prevent excessive leakage, and yet not so heavy as to diminish unduly the ascensional power of the balloon. The first balloon, constructed by the brothers Montgolfier in 1783, was made of cotton fabric lined with paper and sewn on to a network of string. Faujas de Saint-Fond, who published a description of the experiment the same year, says that the gas escaped rapidly. Etiemne Montgolfier corroborates this, attributing the escape chiefly to the needle-holes in the envelope. Had the balloon not been of large size, 35 feet high and containing 22,000 cubic feet of air, it would probably have descended before the lapse of the ten minutes that the experiment lasted.