Engineers and Mechanics Encyclopedia 1839: Railways: George Cayley
In October, 1825, Sir George Cayley, of Brompton, in Yorkshire, obtained letters patent for a locomotive apparatus on the same principle as John Richard Barry but somewhat differently applied.
An elevation of this machine is given in the following eta; a-a represent a side view of the fore and hind running wheels of the carriage, the axletrees of which are made fast to the inclined ends of the waggon box b; each of the two pair of wheels have deep grooves c-c in their peripheries, and into these a stout endless chain d-d is passed around, so as to connect the fore and hind wheels together on the opposite side of the carriage.
To show the groove c, one of the wheels is represented with one of the side flanges removed. Each link of the chain carries two perpendicular arms, which serve as the carrier or bearings to a small roller e-e, which revolves at right angles to the running wheels. These rollers, which form a continuous series on both sides of the carriage, come successively in contact with the ground as the machine is moved in its course, and step over the obstacles that may in their paths. But in the case of any of the rollers alighting on a prominent stone, which might cause an injurious strain upon the machine, a solid wheel or roller f is fixed midway between the wheels on each side of the carriage, which receive and are capable of sustaining the pressure. In order that the carriage may be moved sideways, the rollers are placed at right angles with the running wheels.
The patentee has introduced into his specification some ingenious contrivances for keeping the wheels in a straight path upon unlevel surfaces; but as these do not possess a very practical character, we most refer the reader to the specification for the particulars of them.