The first experiments of David Gordon, who in 1819 was working with William Murdock, in Soho, were for the purpose of using compressed air for common road locomotives. He also invented a portable gas apparatus, and originated a society of gentlemen, with the intention of forming a company for the purpose of running a mail coach and other carriages by means of a high-pressure engine, or of a gas vacuum or pneumatic engine, supplied with portable gas. Alexander Gordon, his son, states that "the committee of the society had only a limited sum at their disposal, nor were there to be more funds until a carriage had been propelled for a considerable distance at the rate of ten miles an hour." David Gordon then tried to prevail upon the committee to make use of a steam engine, but evidently without success. In 1821 he took out a patent for improvements in wheel carriages, and his locomotive is fully described in the interesting Treatise on Elemental Locomotion, by Mr. Alexander Gordon. The machine consisted of a large hollow cylinder about nine feet in diameter and five long, having its internal circumference provided with a continuous series of cogged teeth, into which were made to work the cogged running wheels of a locomotive steam engine, similar to that of Trevithick. The steam power being communicated to the wheels of the carriage, caused them to revolve, and to climb up the internal rack of the large cylinder. The center of gravity of the engine being thus constantly made to change its position, and to throw its chief weight on the forward side of the axis of the cylinder, the latter was compelled to roll forward, propelling the vehicle before it, and whatever train might be added. Gordon's next attempt to construct locomotive carriages for the common road was in 1824. The means proposed was a modification of the method invented by William Brunton. But instead of the propellers being operated upon by the alternating motion of the piston-rod, as in Brunton's vehicle, Gordon contrived to give them a continuous rotatory action and to apply the force of the engines in a more direct manner. The carriage ran upon three wheels, one in the front to steer by, and two behind to bear the chief weight. Each of the wheels had a separate axle, the ends of which had their bearings upon parallel bars, the wheels rolling in a perpendicular position. This arrangement, by avoiding the usual cross-axle, afforded an increased uninterrupted space in the body of the vehicle.