In 1829 Mr. Perkins obtained a patent for the following mode of propelling, which may be considered as an example of sculling motion. Mr. Perkins places each of his paddles on the extremity of a radiating arm, in such a position that its plane if produced towards the centre of motion, would make with the axis of the paddle-wheel an angle of 45°. The axes of the paddle-wheels are not carried across the vessel, in the customary manner, but are carried in a direction sloping towards the stern, and they meet in a point in a straight line from stem to stern along the middle of the vessel, making with it an angle of 45° each, and with each other of 90°. On the extremity of the axis are fixed bevel wheels, which act upon each other, and are both acted upon by an intermediate wheel in connexion with the steam engine or first mover.
By this arrangement, the surface of each paddle, when immersed in the water at its greatest depth, is perpendicular to the side of the vessel, or to the line of motion, as represented at c, in the annexed figure in the marginal cut; at their greatest elevation, each paddle is parallel to the line of motion, as at e; and when in the horizontal position, whether ascending or descending, the paddles present an angle of about 45°; and, from the angle it deviates but little when in the act of entering or leaving the water, as the patentee proposes to immerse the wheel to about one-fourth of its diameter. The annexed figure is intended to represent the outline, in plan, of a vessel with these paddles attached. At a is the boat, b b, the paddle axle, to which a uniform motion is given through the medium of the bevel gear which connects them; c c are two of the paddles immersed in the water, and in the act of propelling; d d, e e, andff, are those paddles which succeed each other in the revolution. The ohlique action of the blades of the paddle, as they perform their revolutions, will be understood by reference to the cut before explained.