The principal reason for Stevens’ failure with the screw propeller was that there were no tools or competent workmen in America to construct properly the steam-engines that he planned between 1800 and 1806, and success was therefore impossible. He therefore reverted to the paddle-wheel with its slow-moving engine and the boilers then in use, carrying steam at a pressure of two or three pounds above the atmosphere. Stevens was not disposed to abandon the screw entirely, for he presented a plan in 1816 to the United States Government for a warship propelled by that means, but nothing came of it. In the spring of 1825 an advertisement appeared in the _Times_ offering a hundred guineas for a means of propelling vessels without paddles, and in that year a company was formed for applying the gas vacuum engine to canal navigation. [Illustration: THE “Q.E.D.”] Some of the earlier steam-engine-propelled iron vessels were strange craft. Designers and builders felt that they were entering upon new ground, and being less trammelled by tradition allowed their fancy free play. Their plans were occasionally daring in their originality and came astonishingly near to achieving success. A freakish-looking vessel was launched on July 15, 1844, from the yard of her owner and builder, Mr. Cootes, at Walker-on-Tyne. She was a collier, built of iron, and carried a screw propeller driven by a small engine. On this account she is said to have been the first iron screw collier, antedating by some years the _John Bowes_, to which the honour is usually given. This ship was confessedly an experiment and was named the _Q.E.D._, and as her name was not changed during her career she no doubt gave satisfaction. The sea-borne coal trade was largely confined to wooden brigs of comparatively small tonnage. The _Q.E.D._ was barque-rigged, “with taut masts and square yards, the masts raking aft in a manner that is seldom seen except in the waters of the United States. She was provided with a 20-horse-power engine by Hawthorn, which turned a propeller (screw), a compound of several inventions, having four flies or flaps at right angles with each other, the bend of each flap at an angle of 45 degrees from the centre.” On her first voyage to London,[82] when she had about twenty keels of coal on board, she grounded on the Gunfleet Sands, but was refloated undamaged after some of her cargo had been thrown overboard. [82] Mr. Charles Mitchell, afterwards head of the shipbuilding firm which amalgamated with Sir W. G. Armstrong and Co. under the style of Armstrong, Mitchell and Co., Ltd., went to sea in this vessel for one or two voyages, to watch the behaviour of her engines.--“The Making of the River Tyne,” by L. W. Johnson.