Paddle-wheels for driving boats through the water were used long before steam-engines were thought of.
They were worked by hand and foot-power without, however, any advantage over the old-fashioned oar.
The horse-boat, in a variety of forms, has been in use for many years, and is not yet quite obsolete.
In its earlier form two horses, one on each side of a decked scow,
were hitched to firmly braced upright posts at which they tugged for all they were worth without ever advancing beyond their noses,
but communicating motion to the paddle-wheels by the movable platform on which they trod.
For larger boats four or five horses were harnessed to horizontal bars converging towards the centre, and moved around the deck in a circle,
the paddles receiving their impulse through a set of cog-wheels.