While Ericsson was thus employed, Mr. Thomas Pettit Smith, who, on the 31st May, 1836, had taken out a patent for a “sort of screw or ‘worm,’ made to revolve rapidly under water in a recess or open space formed in that part of the after-part of the vessel commonly called the dead rising or dead wood of the stern,” was experimenting, and the following year exhibited it in practical form in a small vessel. It appeared to several gentlemen so satisfactory that a company was formed in July, 1839, to purchase the patent. It was now applied to a vessel called the _Archimedes_, the burden of which was 237 tons, and although her speed was somewhat less than Ericsson’s vessel, the trial was undeniably satisfactory, more especially as it was obvious that her engine was really not large enough for a propeller of the size. In her next trials against the _Widgeon_, the fastest paddle-wheel steamer then running between Dover and Calais, the success of the screw might be regarded as an established fact. The _Archimedes_ laboured under the disadvantage of having ten horse-power less steam, while her burden was seventy-five tons more; she had the advantage of carrying more sail. On the first three trials the _Widgeon_ had a very slight advantage, in spite of her superior steam-power and smaller tonnage, while on the last two the _Archimedes_ made the trip in less time than it had ever previously been performed by any of the mail packets. Captain Chappell, R.N., afterwards took her clear round England and Scotland, calling at numerous ports. The Admiralty at length ordered the construction of a screw vessel, and the lines of the _Rattler_ were laid down on the same model as the _Alecto_, a paddle-wheel steamer then building. Another claimant as an inventor, who should be mentioned most honourably, is Mr. Woodcroft, some of whose experiments were being patented in 1826. They were not tried on a suitable scale till after the successes of Ericsson and Smith. Woodcroft’s “varying pitch screw-propeller,” patented in 1844, the title of which describes itself, is to-day “considered the best and most useful type.”