Note 48 — Chapter IV · Thomas Newcomen—The Atmospheric Engine.

In describing his mode of obtaining rotary motion by ratchet wheels, a weight, and ropes, Hulls states that he uses two axes, one behind the other, each of which is essential to the object; and he then adds, that when his tow-boat is to be used in shallow rivers, the machine works by two cranks fixed to the hindermost axis; to which cranks are fixed two shafts (or poles) of proper length to reach the bottom of the river, and which move alternately forward from the motion of the wheels by which the vessel is carried on: so that the cranks, as described by Hulls, receive rotary motion from the axis on which they are placed, and do not, as has been erroneously stated, impart that motion to it.—Bennet Woodcroft, ‘Sketch of the Origin and Progress of Steam Navigation.’ London, 1848.