word, when publicly discussed, the general opinion was that the vast loss of mechanical power would prevent it from being employed as a substitute for the now old-fashioned paddle-wheel![138] [Sidenote: Mr. T. P. Smith.] While Ericsson was making his experiments in the _Francis B. Ogden_, Mr. Thomas Pettit Smith, who, on the 31st of 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,”[139] was also at work with his invention, and, in the following year, put it into practical operation. His first trial, made in a small vessel of 6 tons burden, with an engine the cylinder of which was 6 inches diameter and 15 inches stroke, was considered by a few far-seeing persons so satisfactory,[140] that they applied for, and obtained on the 29th of July, 1839, an Act of Parliament for incorporating a company called the Steam Ship Propeller Company, to enable them to purchase “certain letters patent,” that is, the screw-propeller of T. P. Smith. [Sidenote: The _Archimedes_.] [Sidenote: Her trial with the _Widgeon_, Oct. 1839,] The first successful application of this screw-propeller, on a large scale, was to a vessel called the _Archimedes_, constructed under the direction of the patentee of the screw, Mr. Smith. Her burden was 237 tons, and her mean draught of water 9 feet 4 inches; the diameter of the cylinder 37 inches, and the length of the stroke of the piston 3 feet; her screw-propeller consisted of two half threads of an 8 feet pitch, 5 feet 9 inches in diameter; each was 4 feet in length, and they were placed diametrically opposite to each other, at an angle of about 45 degrees on the propeller shaft. The propeller itself passed through a hole cut in the dead wood, immediately before the rudder; the keel being continued under the screw. The performance of the engines averaged twenty-six strokes per minute, the revolutions of the screw at the same time being 138⅖. The calculations of the inventor were that, provided there was no slip or recession, the vessel ought to advance 8 feet for every revolution of the screw, or 12·60 miles per hour. But the utmost speed ever obtained by the _Archimedes_, under the power of steam alone, was 9·25 nautical miles per hour, showing a loss by recession of rather less than one-sixth under the most favourable circumstances. The _Archimedes_ was not, however, a fair illustration of the screw-propelling principle, as her steam-power was not great enough to drive a screw sufficient for the size of the vessel. Nevertheless, in her subsequent trials from Dover to Calais against the _Widgeon_, the fastest paddle-steamer on the station, the superior value of the screw-propeller was proved. Although in the first three or four experiments the _Widgeon_ had the advantage by a few minutes,