In this engine, high-pressure steam was employed, and the condenser was dispensed with. The boiler was of the form devised by Evans, and was subsequently generally used in Cornwall, where it was called the "Trevithick Boiler." The engine had but one cylinder, and the piston-rod drove a "cross-tail," working in guides, which was connected with a "cross-head" on the opposite side of the shaft by two "side-rods." The connecting-rod was attached to the cross-head and the crank, "returning" toward the cylinder as the shaft lay between the latter and the cross-head. This was probably the first example of the now common "return connecting-rod engine." The connection between the crank-shaft and the wheels of the carriage was effected by gearing. The valve-gear and the feed-pumps were worked from the engine-shaft. The inventor proposed to secure his wheels against slipping by projecting bolts, when necessary, through the rim of the wheel into the ground. The first carriage of full size was built by Trevithick and Vivian at Camborne, in 1803, and, after trial, was taken to London, where it was exhibited to the public. _En route_, it was driven by its own engines to Plymouth, 90 miles from Camborne, and then shipped by water. It is not known whether the inventor lost faith in his invention; but he very soon dismantled the machine, sold the engine and carriage separately, and returned to Cornwall, where he soon began work on a railroad-locomotive. In 1821, Julius Griffiths, of Brompton, Middlesex, England, patented a steam-carriage for the transportation of passengers on the highway. His first road-locomotive was built in the same year by Joseph Bramah, one of the ablest mechanics of his time. The frame of the carriage carried a large double coach-body between the two axles, and the machinery was mounted over and behind the rear axle. One man was stationed on a rear platform, to manage the engine and to attend to the fire, and another, stationed in front of the body of the coach, handled the steering-wheel. The boiler was composed of horizontal water-tubes and steam-tubes, the latter being so situated as to receive heat from the furnace-gases _en route_ to the chimney, and thus to act as a superheater. The wheels were driven, by means of intermediate gearing, by two steam-engines, which, with their attachments, were suspended on helical springs, to prevent injury by jars and shocks. An air-surface condenser was used, consisting of flattened thin metal tubes, cooled by the contact of the external air, and discharging the water of condensation, as it accumulated within them, into a feed-pump, which, in turn, forced it into the lowest row of tubes in the boiler. The boiler did not prove large enough for continuous work; but the carriage was used experimentally, now and then, for a number of years.