When there was so much difference of opinion among those passing as experts as to the respective merits of the paddle-wheel steamer and the steamer driven by a screw propeller, the Admiralty decided to settle the controversy by pitting representative vessels against each other and noting the result. Accordingly the _Rattler_ was selected to champion the screw, and the _Alecto_ the paddle-wheel. [Illustration: THE TRIAL OF SCREW _v._ PADDLE--H.M. SLOOPS “RATTLER” AND “ALECTO” TOWING STERN AND STERN.] The _Alecto_ was a paddle sloop, driven by direct acting engines, but otherwise was a very similar vessel to her screw rival. The two vessels were fastened stern to stern, and ordered to steam ahead. The screw steamer won the novel tug of war, the _Alecto_ being towed stern foremost. This remarkable encounter took place in the North Sea, on April 3rd, 1845, in calm weather. A more important tug of war was that on June 20th, 1849, when the screw corvette _Niger_ was pitted against the paddle sloop _Basilisk_ in the Channel, and again the screw boat was victorious. The _Trident_ was the first iron steamship of war ordered by the Admiralty, and the first ever built. She was launched from Messrs. Ditchburn and Mare’s yard, at Blackwall, in December, 1845, and in the shape of her hull followed the lines of a sailing ship of the same size. Her length over all was 200 feet, and between the perpendiculars 180 feet; her beam was 31 feet 6 inches, and over the paddle-boxes 52 feet 6 inches, and her burthen was 900 tons. She had engines of 330 h.p., with oscillating cylinders and tubular boilers, so that altogether she was an important vessel in the constructional development of the British navy. She was very strongly put together, as her ribs were double, each rib being composed of two angle irons, 4 inches by 3½ inches by ½ inch thick, riveted together, and in one entire length from the gunwale to the keel she having a total of two hundred and seventy pairs of these double ribs. The iron skin was ¾ inch thick at the keel, and diminished to ½ inch at the gunwale. She was to carry two long swivel guns of 10-inch bore, one fore and one aft, to fire in line of keel, and four 32-pounder guns to fire on the broadside.