Double ship, 1787.

Lithograph by C F Cheffins after a drawing by John C Bourne, of a 'double vessel, sixty-feet deck, propelled by two wheels, turned by two men each', built by Patrick Miller (1731-1815). Human stamina, however, proved inadequate for propulsion of such a vessel, and Miller later commissioned mining engineer William Symington (1763-1831) to build a steam engine to power another experimental craft. Illustration from 'A sketch of the origin and progress of steam navigation from authentic documents' by steam navigation pioneer Bennet Woodcroft (1803-1879) published in London in 1848.