In 1780, Smeaton had a list of 18 large engines working in Cornwall. The larger number of them were built by Jonathan Hornblower and John Nancarron. At this time, the largest and best-known pumping-engine for water-works was at York Buildings, in Villiers Street, Strand, London. It had been in operation since 1752, and was erected beside one of Savery's engines, built in 1710. It had a steam-cylinder 45 inches in diameter, and a stroke of piston of 8 feet, making 7-1/2 strokes per minute, and developing 35-1/2 horse-power. Its boiler was dome-shaped, of copper, and contained a large central fire-box and a spiral flue leading outward to the chimney. Another somewhat larger machine was built and placed beside this engine, some time previous to 1775. Its cylinder was 49 inches in diameter, and its stroke 9 feet. It raised water 102 feet. This engine was altered and improved by Smeaton in 1777, and continued in use until 1813. Smeaton, as early as 1765, designed a _portable_ engine,[33] in which he supported the machinery on a wooden frame mounted on short legs and strongly put together, so that the whole machine could be transported and set at work wherever convenient. [33] Smeaton's "Reports," vol. i., p. 223. [Illustration: FIG. 23.--Smeaton's Portable-Engine Boiler, 1765.] In place of the beam, a large pulley was used, over which a chain was carried, connecting the piston with the pump-rod, and the motion was similar to that given by the discarded beam. The wheel was supported on A-frames, resembling somewhat the "gallows-frames" still used with the beam-engines of American river-boats. The sills carrying the two A's supported the cylinder. The injection-cistern was supported above the great pulley-wheel. The valve-gearing and the injection-pump were worked by a smaller wheel, mounted on the same axis with the larger one. The boiler was placed apart from the engine, with which it was connected by a steam-pipe, in which was placed the "regulator," or throttle-valve. The boiler (Fig. 23) "was shaped like a large tea-kettle," and contained a fire-box, _B_, or internal furnace, of which the sides were made of cast-iron. The fire-door, _C_, was placed on one side and opposite the flue, _D_, through which the products of combustion were led to the chimney, _E_; a short, large pipe, _F_, leading downward from the furnace to the outside of the boiler, was the ash-pit. The shell of the boiler, _A_, was made of iron plate one-quarter of an inch thick. The steam-cylinder of the engine was 18 inches in diameter, the stroke of piston 6 feet, the great wheel 6-1/2 feet in diameter, and the A-frames 9 feet high. The boiler was made 6 feet, the furnace 34 inches, and the grate 18 inches in diameter. The piston was intended to make 10 strokes per minute, and the engine to develop 4-1/8 horse-power.