The late Dr. Birkbeck, in a letter addressed to the 'Mechanics' Register,' in the year 1824, claimed that John Swan, of 82, Mansfield Street, Kingsland Road, London, was the practical inventor of the screw propeller. John Swan was a native of Coldingham, Berwickshire. He had removed to London, and entered the employment of Messrs. Gordon, of Deptford. Swan fitted up a boat with his propeller, and tried it on a sheet of water in the grounds of Charles Gordon, Esq., of Dulwich Hill. "The velocity and steadiness of the motion," said Dr. Birkbeck in his letter, "so far exceeded that of the same model when impelled by paddle-wheels driven by the same spring, that I could not doubt its superiority; and the stillness of the water was such as to give the vessel the appearance of being moved by some magical power." Then comes another claimant--Mr. Robert Wilson, then of Dunbar (not far from Coldingham), but afterwards of the Bridgewater Foundry, Patricroft. In his pamphlet, published a few years ago, he states that he had long considered the subject, and in 1827 he made a small model, fitted with "revolving skulls," which he tried on a sheet of water in the presence of the Hon. Capt. Anthony Maitland, son of the Earl of Lauderdale. The experiment was successful--so successful, that when the "stern paddles" were in 1828 used at Leith in a boat twenty-five feet long, with two men to work the machinery, the boat was propelled at an average speed of about ten miles an hour; and the Society of Arts afterwards, in October, 1882, awarded Mr. Wilson their silver medal for the "description, drawing, and models of stern paddles for propelling steamboats, invented by him." The subject was, in 1833, brought by Sir John Sinclair under the consideration of the Board of Admiralty; but the report of the officials (Oliver Lang, Abethell, Lloyd, and Kingston) was to the effect that "the plan proposed (independent of practical difficulties) is objectionable, as it involves a greater loss of power than the common mode of applying the wheels to the side." And here ended the experiment, so far as Mr. Wilson's "stern paddles" were concerned.