9 Feb. 1808. He was educated at a private school at Ashford in Kent, and began life as a grazing farmer in Romney Marsh, afterwards removing to Hendon, Middlesex. In boyhood Smith acquired great skill in the construction of model boats, and displayed much ingenuity in contriving methods of propulsion for them. Continuing to devote much of his spare time to the subject, he in 1835 constructed a model which was propelled by a screw, actuated by a spring, and which proved so successful that he became convinced that this form of propeller would be preferable to the paddle-wheels at that time exclusively employed.
The scheme of using some form of screw as a propeller had been advocated by Robert Hooke [q. v.] as early as 1681, and by Daniel Bernouilli and others in the eighteenth century. On 9 May 1795 Joseph Bramah [q. v.] took out a patent for a screw propeller, but did not apparently construct one. But between 1791 and 1807 John Cox Stevens, an American mechanician, made practical experiments with a steam-boat propelled by a screw at Hoboken, New Jersey. Moreover, simultaneously with Smith's first efforts, Captain John Ericsson, a Swede, was actively working in the same direction.
Smith was wholly ignorant of these endeavours. Impressed with the importance of the appliance, of which he believed himself the sole discoverer, he practically abandoned his farming, and devoted himself with whole-hearted enthusiasm to the development and perfecting of his idea.
By the following year (1836) he had constructed a superior model, which was exhibited in operation to friends upon a pond on his farm at Hendon, and afterwards to the public at the Adelaide Gallery, London. On 31 May in the same year he took out a patent, based upon this model, for ‘propelling vessels by means of a screw revolving beneath the water at’ the stern. Six weeks later, on 13 July—it is curious to note—Captain Ericsson took out, also in London, a similar patent. Smith quickly perfected his invention. With the pecuniary assistance of Mr. Wright, a banker, and the technical assistance of Mr. Thomas Pilgrim, a practical engineer whose services Smith engaged, he soon constructed a small boat of ten tons burden and fitted her with a wooden screw of two turns, driven by an engine of about six horse-power. This was exhibited to the public in operation in November 1836. An accident to the propeller led him to the conclusion that a shortened screw would give more satisfactory results, and in 1837 a screw of a single turn was fitted. With a view to proving the efficiency of this method of propulsion under all circumstances, the little vessel was taken to Ramsgate, thence to Dover and Hythe, returning in boisterous and stormy weather. The propeller proved itself efficient to an unexpected degree in both smooth and rough water.
The attention of the admiralty was now invited to the new invention, to which at the outset the sentiment of the engineering world was almost universally opposed. The admiralty considered it to be desirable that experiments should be made with a larger vessel before recommending the adoption of the screw in the navy. Accordingly a small company was formed, and the construction of a new screw steamer, the Archimedes, resolved upon. This was a vessel of 237 tons, fitted with a screw of one convolution, propelled by engines of eighty horse-power, the understanding with the admiralty being that her performance would be considered satisfactory if a speed of five knots an hour were maintained. Double this speed was actually achieved, and the vessel, after various trials on the Thames and at Sheerness, proceeded to Portsmouth, where she was tried against the Vulcan, one of the fastest paddle steamers in her majesty's service, with the most gratifying result. This was in October 1839, and in the following year the admiralty experts deputed to conduct a series of experiments with her reported that they considered the success of the new propeller completely demonstrated. The admiralty would not even then, however, definitely commit themselves, and it was not until a year later—in 1841—that orders were given for the Rattler, the first war screw steamer in the British navy, to be laid down at Sheerness. In the meantime the Archimedes was taken to the principal ports in Great Britain, to Amsterdam, and across the Bay of Biscay to Oporto, everywhere exciting interest, and leaving the impression that the value of the screw had been fully proved. When at Bristol Isambard Kingdom Brunel [q. v.] was invited to visit the vessel, and he was so satisfied with the new propeller that the Great Britain, the first large iron ocean-going steamer, which was originally intended to be fitted with paddles, was altered to adapt her for the reception of a screw. The Rattler was launched in 1843, and on 18 March 1844 Smith's four-bladed screw was tested in her with complete success. Orders were soon given for twenty war vessels to be fitted with it under Smith's superintendence. The hitherto accepted theory that the screw could not economically compete with the paddle because of the loss of power arising from the obliquity