Bramah also applied the rotary principle to the fire-engine. He studied the principles of hydraulics, and introduced many improvements into machinery for pumping, a rotary principle being one of them. He attained this object by changing the form of the cylinder and piston, the part acting directly on the water being shaped as a "slider," and working round a cavity in form of a cylinder, and maintained in its place by a groove. He applied the rotative principle to many objects, one being the fire-engine. His fire-engine was patented in 1793; but we cannot discover that it changed any vital principle of the machine, which, as we have seen, consists in essence of a movable force-pump, steadied and strengthened by a compressed air-chamber and a flexible delivery-hose. Joseph Bramah, however, is doubtless best known to fame as the inventor of the hydraulic press, though he is also celebrated for the safety-lock which bears his name. He was a farmer's son, and was born at Stainborough in Yorkshire in 1748; but an accident rendering him lame, he was apprenticed to a carpenter. Engaging in business as a cabinet-maker in London, he was employed one day to fit up some sanitary appliances, and their imperfections led him to devise improvements. He took out his first patent in 1778 and this contrivance proved to be the first of a long series. His lock followed, and then, assisted in one detail by Henry Maudslay, he introduced his hydraulic press, a machine which he foresaw was capable of immense development. Several of his improvements are concerned with water, such as contrivances connected with pumps and fire-engines, and with building boilers for steam-engines. It is also said he was one of the first proposers of the screw-propeller for steamships. Altogether, he was the author of eighteen patents; though it has been pointed out that he improved and applied the inventions of others, rather than originated the whole thing himself. While he contributed improvements to the fire-engine, the vital principle of the air-chamber and the flexible hose remained the same. Up to about the year 1832, the larger engines generally in use in London seem to have thrown some eighty-eight gallons a minute from fifty to seventy feet high. The next notable development was the application of steam to work the force-pumps. But this addition, which was made about 1830 by John Braithwaite, also did not alter the principle of the air-chamber. John Braithwaite came of an engineering family. He was born in 1797, the third son of John Braithwaite, the constructor of one of the first diving-bells. The ancestors of the Braithwaites had conducted an engineer's business, or something analogous to it, at St. Albans ever since the year 1695.