Lithograph of HM Steam Sloops 'Rattler' and 'Alecto' towing stern to stern for the purpose of testing the relative powers of the screw propeller and the paddle-wheel. The trial was made in the North Sea during a perfect calm on 3rd April, 1845, on which occasion the Rattler towed the Alecto sternforemost at the rate of two miles and eight tenths per hour. Both vesels exerting their full power in opposite directions'. This trial could not be argued as having definitively proved the superiority of screw steamers over paddle-wheel vesels, as the Rattler's engines produced 300 hp compared to only 141 hp for those of the Alecto.
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