The Admiralty thought so little of steam engines at first that it did not trouble to record the names of its early steamers in the navy list. Owing to the representations of Marc Isambard Brunel, the Admiralty consented to try steam, and experimented with two small paddle-boats, the _Monkey_, built at Rotherhithe in 1821, and the _Comet_, built at Deptford in 1822, which were acquired to be used as tugs or despatch boats. The former was a vessel of 210 tons, and had engines of 80 nominal h.p.[29] by Messrs. Boulton and Watt. The two cylinders were each about 35½ inches diameter, with a stroke of 3 feet 6 inches, and, working at 26½ revolutions per minute, gave a mean piston speed of 185 feet per minute. It will be interesting and instructive to contrast these figures with those of the latest engines in warships, which will be found in another chapter. The _Active_ and _Lightning_ followed in 1822 and 1823 respectively, their names appearing together with a few others for the first time in the official navy list for March, 1828.[30] None of these steamers, however, could be classed as war vessels. From this year to 1840 seventy other steam vessels were added to the navy. All the early steamers were built in private yards, and the contractors had even to provide the engine-room staffs, which were taken over together with the steamers. By 1832, the Admiralty bestirred itself and built its first steamer, the _Salamander_, but until 1840 none was over 1,000 tons, and all were of wood, propelled by paddle engines, and such guns as some of them carried were small and ineffective. With the increase of the size of the vessels came a more than corresponding increase in the power of the engines. The _Rhadamanthus_, for instance, built in 1832, had engines capable of being worked up to 400 indicated h.p., though they were of 200 h.p. nominal. The safety valves carried a load of 4 lb. to the square inch, and the total weight of the machinery was 275 tons. In 1839, five wooden steamers were built for the Admiralty, and two of them, the _Hecla_ and _Hecate_, of 817 tons, and 250 h.p. each, were sent to Scott’s, at Greenock, to be engined, and were the first naval vessels to have their machinery fitted on board in Scotland.