He exhibited a model of his invention at the Polytechnic Institution. The propelling principle, or power, was here, also, applied to interrupted surfaces, or vanes, put in revolution. These vanes were four in number, but were found entirely ineffectual in moving the balloon, or in aiding its ascending power. The whole project was thus a complete failure.

It was at this juncture that Mr. Monck Mason (whose voyage from Dover to Weilburg in the balloon Nassau occasioned so much excitement in 1837) conceived the idea of employing the principle of the Archimedean screw for the purpose of propulsion through the air—rightly attributing the failure of Mr. Henson's scheme, and of Sir George Cayley's to the interruption of surface in the independent vanes. He made the first public experiment at Willis's Rooms, but afterward removed his model to the Adelaide Gallery.

Like Sir George Cayley's balloon, his own was an ellipsoid. Its length was 13 feet 6 inches—height, 6 feet 8 inches . It contained about 320 cubic feet of gas, which, if pure hydrogen, would support 21 pounds upon its first inflation, before the gas has time to deteriorate or escape. The weight of the whole machine and apparatus was 17 pounds—leaving about 4 pounds to spare. Beneath the centre of the balloon, was a frame of light wood, about 9 feet long, and rigged on to the balloon itself with a net-work in the customary manner. From this framework was suspended a wicker basket or car.

The screw consists of an axis of hollow brass tube, 18 inches in length, through which, upon a semi-spiral inclined at 15 degrees, pass a series of steel-wire radii, 2 feet long, and thus projecting a foot on either side. These radii are connected at the outer extremities by 2 bands of flattened wire; the whole in this manner forming the framework of the screw, which is completed by a covering of oiled silk cut into gores, and tightened so as to present a tolerably uniform surface.