In 1836 Captain Ericsson, a Swedish gentleman, well known for his mechanical talent, obtained a patent for an apparatus for propelling steam vessels. The invention consists in a modification of the water screw, or spiral propeller; but applied in a different manner to what has been usually proposed. Fig. 1 is an end view, and fig. 2 a side view of the apparatus. Upon a broad cylindrical hoop a of wrought iron are placed light fans or vanes b, in an oblique, or rather a spiral direction, as the wheel may in fact be considered as a short portion of a screw of eight threads, the rake of which is about equal to the external circumference; or one turn of the screw would advance it through a space equal to the circumference. These fans are firmly riveted to the hoop a, and also to a narrow hoop c at their outer edges; and the hoop c is connected to its shaft by three broad wrought-iron arms d, set at such an angle as to offer the least possible resistance to the passage of the wheel through the water.
Two of these wheels are suspended from the stern, by a strong framing e; the shaft of the outermost wheel passes through the shaft of the inner wheel (which is made hollow to receive it); and both shafts pass through an iron socketf, in the stern post, and through a stuffing boxg, fixed on the stern post within the vessel, to prevent the entrance of the water. The set of vanes upon the two wheels stand in opposite directions; and the two shafts are connected to the engine in such a manner that the two revolve in contrary directions, and the outer wheel about one sixth faster than the inner one. As the shafts pass through the rudder, the upper and lower portions are connected by a broad iron stay h on each side, of such form as to allow the necessary vibration of the rudder. The wheels are entirely immersed under the water.