underwater on its own, and powered by compressed air. The result was a submarine weapon, the Minenschiff ("mine ship"), the first modern self-propelled torpedo, officially presented to the Austrian Imperial Naval commission on December 21, 1866. The first trials were not successful as the weapon was unable to maintain a course on a steady depth. After much work, Whitehead introduced his "secret" in 1868 which overcame this. It was a mechanism consisting of a hydrostatic valve and pendulum that caused the torpedo's hydroplanes to be adjusted so as to maintain a preset depth. First torpedo boats During the mid-19th century, the ships of the line were superseded by large steam powered ships with heavy gun armament and heavy armour, called ironclads. Ultimately this line of development led to the dreadnought class of all-big-gun battleship, starting with . At the same time, the weight of armour slowed the battleships, and the huge guns needed to penetrate enemy armour fired at very slow rates. This allowed for the possibility of a small and fast ship that could attack the battleships, at a much lower cost. The introduction of the torpedo provided a weapon that could cripple, or even sink, any battleship. The first warship of any kind to carry self-propelled torpedoes was HMS Vesuvius of 1873. The first seagoing vessel designed to fire the self-propelled Whitehead torpedo was . The boat was built by John Thornycroft at Church Wharf in Chiswick for the Royal Navy. It entered service in 1876 and was armed with self-propelled Whitehead torpedoes. As originally built, Lightning had two drop collars to launch torpedoes; these were replaced in 1879 by a single torpedo tube in the bow. She carried also two reload torpedoes amidships. She was later renamed Torpedo Boat No. 1. The French Navy followed suit in 1878 with Torpilleur No 1, launched in 1878 though she had been ordered in 1875. Another early such ship was the Norwegian warship , ordered from Thornycroft shipbuilding company, England, in either 1872 or 1873, and built at Thornycroft's shipyard at Church Wharf in Chiswick on the River Thames. Managing a speed of , she was one of the fastest boats afloat when completed. The Norwegians initially planned to arm her with a spar torpedo, but this may never have been fitted. Rap was outfitted with launch racks for the new self-propelled Whitehead torpedoes in 1879. Use in combat In