Meanwhile he applied himself with his accustomed energy to the practical working out of another favorite idea. The principle of the Ericsson propeller was first suggested to the inventor by a study of the means employed to propel the inhabitants of the air and deep. He satisfied himself that all such propulsion in Nature is produced by oblique action; though, in common with all practical men, he at first supposed that it was inseparably attended by a loss of power. But when he reflected that this was the principle invariably adopted by the Great Mechanician of the Universe, in enabling the birds, insects, and fishes to move through their respective elements, he knew that he must be in error. This he was soon able to demonstrate, and he became convinced, by a strict application of the laws which govern matter and motion, that no loss of power whatever attends the oblique action of the propelling surfaces applied to Nature's locomotives. After having satisfied himself on the theory of the subject, the first step of the inventor was the construction of a small model, which he tried in the circular basin of a bath in London. To his great delight, so perfectly was his theory borne out in practice, that this model, though less than two feet long, performed its voyage about the basin at the rate of three English miles an hour. The next step in the invention was the construction of a boat forty feet long, eight feet beam, and three feet draught of water, with two propellers, each of five feet three inches in diameter. So successful was this experiment, that, when steam was turned on the first time, the boat at once moved at a speed of upwards of ten miles an hour, without a single alteration being requisite in her machinery. Not only did she attain this considerable speed, but her power to tow larger vessels was found to be so great that schooners of one hundred and forty tons' burden were propelled by her at the rate of seven miles an hour; and the American packet-ship Toronto was towed in the river Thames by this miniature steamer at the rate of more than five English miles an hour. This feat excited no little interest among the boatmen of the Thames, who were astonished at the sight of this novel craft moving against wind and tide without any visible agency of propulsion, and, ascribing to it some supernatural origin, united in giving it the name of the _Flying Devil_. But the engineers of London Hoarded the experiment with silent neglect; and the subject, when laid before the Lords of the British Admiralty, failed to attract any favorable notice from that august body.