[39] Ibid., 1709, p. 282.
[40] Gill’s “Technical Repository,” 1829, p. 251.
[41] “Specifications of Marine Propulsion,” Woodcroft, vol. i. p. 21.
[42] The reader will find this plan described at length in Woodcroft’s “Specifications of Marine Propulsion,” pp. 23 and 34 (note). Hulls “placed a paddle-wheel on beams projecting over the stern, and it was turned by an atmospheric steam-engine acting in conjunction with a counterpoise weight upon a system of ropes and grooved wheels” (MacGregor).
[43] Jonathan Hulls was born at Campden, in Gloucestershire, in 1699, and made his first experiments on the Avon at Evesham. In 1737 he published a pamphlet entitled “A Description and Draughts of a New Invented Machine;” in this he proposed to put a Newcomen engine on board a tow-boat to work a paddle-wheel placed in the stern.
Mr. Smiles (“Lives of Boulton and Watt,” p. 63) observes, “It has been stated that Newcomen took out a patent for his invention in 1705;” but this is a mistake, as no patent was ever taken out by Newcomen. It is supposed that Savery, having heard of his invention, gave him notice that he would regard his method of producing a vacuum as an infringement of his patent, yet the principle on which Newcomen’s engine worked was entirely different from that of Savery.
[44] He died shortly after his arrival at Venice, and his plans were never put into practical operation.
[45] The now well-known principle of a steam-engine is this: there is a cylinder with its rod fixed to one end of a lever, which is worked by the combined pressure of the atmosphere and the steam upon a piston, a temporary vacuum being made below it by suddenly condensing the steam, which had been let into the cylinder where this piston works, by a jet of cold water thrown into it. A partial vacuum being thus made, the weight of the atmosphere presses down the piston and raises the other end of the straight lever, thereby drawing up water from a mine, or, by the numberless improvements made of late years, communicating a mechanical power which may set in motion every description of machinery.
[46] “Woodcroft on Steam Navigation,” p. 14; “Cabinet Cyclopædia,” Mechanics, p. 258.
[47] Letter to Dr. Small, with a drawing; Muirhead’s “James Watt,” London, 1854, vol. ii. pp. 4, 8, 11.