The best form of screw having been determined, it still remained to compare the screw propeller with the paddlewheel. Accordingly the _Alecto_, a paddlewheel sloop of similar lines to the _Rattler_, was selected as the protagonist of the older form of propulsion, while the _Rattler_ herself represented the screw. Naval opinion was still completely divided on the great question, while in the competing sloops the utmost emulation existed, each captain advocating his own type of propeller. The speed trials took place, and showed the _Rattler_ to have an undoubted advantage. The paddlewheel, however, laid claim to a superiority in towing power. So a further competition was ordered, as realistic as any, perhaps, in the history of applied science: nothing less than a tug-of-war between Paddle and Screw, those two contending forms of steam propulsion! Lashed stern to stern and both steaming ahead full power, one evening in the spring of ’45 the two steamers struggled for mastery. And as _Rattler_ slowly but surely pulled over _Alecto_, the question which had been for years so hotly debated was settled; the superiority of the screw was demonstrated. With the adoption of the screw the problem of disposing the armament was settled. The broadsides and the spaces between decks were once more free to the guns along the entire length; moreover the action of the screw was in complete harmony with that of the sails. With the screw as an auxiliary to sail power, and subsequently with the screw as sole means of propulsion, a change came over the character of the pivot armament. Whereas with the paddlewheel the pivot gun was the chief means of offence, when the screw was introduced the broadside was restored, and though the heavy pivot guns were retained (steam and the pivot gun had become associated ideas), yet by their comparatively limited numbers they became a subordinate element in the total armament. [Illustration: _RATTLER_ VERSUS _ALECTO_ From an aquatint in the South Kensington Museum]