William Brunton's Locomotive, 1813.
This Locomotive or "Mechanical Traveler" was built by Mr. Brunton of the Butteryby Works, Derbyshire, in 1813. This Engine had two legs attached to the back part, which being alternately moved by the engine, pushed it before them. The legs, or propellers, imitated the legs of a man, or the forelegs of a horse, with joints, and when worked by the machine, alternately lifted and pressed against the ground or road, propelling the engine forward. This Engine moved on a railway at the rate of 2_ miles per hour with the tractive force of 4 horses. The Engine never got beyond the experimental state for on one of its trials it unhappily blew up, killing and wounding several bystanders, was never repaired, and laid by as one of the failures of the times.
A description of how this contraption worked is given in William H. Brown’s The History of the First Locomotives In America.