498 REPORT-- 1881. 



greater number of revolutions per minute, and thus a piston-speed 

 of some 600 to 800 feet per minute is attained ; and this, coupled 

 with the fairly high mean pressure which prevails, enables a large 

 power to be got from a comparatively small-sized engine. Speeds of 

 15 knots an hour are now iu many cases maintained by steam-vessels 

 throughout their voyages, and on trial trips are not uncommonly ex- 

 ceeded. The steam-vessel is now the accepted vessel of war. We 

 have them in an ai-moured state and in an unarmoured state, but when 

 unarmoured rendered so formidable by the power which their speed 

 gives them of choosing their distance, as to make them, when fur- 

 nished with powerful guns, dangerous opponents even to the best 

 armoured vessels. We have also now marine engines governed by 

 governors of such extreme sensitiveness as to give them the semblance 

 of being endowed with the spirit of prophecy, as they appear rather to be 

 regulating the engine for that which is about to take place than for that 

 which is taking place. This may sound a somewhat extravagant state- 

 ment, but it is so nearly the truth that I have hardly gone outside of it, 

 in using the words I have employed. For a marine governor to be of 

 any use it must not wait till the stern of the vessel is out of the water, 

 before it acts to check the engine and reduce the speed ; nothing but the 

 most sensitive and indeed anticipatory action of the governor can effi- 

 ciently control marine propulsion. Instances are on record of vessels 

 having engines without marine governors, being detained by stress of 

 weather at the mouth of the Thames, while vessels having such 

 governors, of good design, have gone to Newcastle, have come back, 

 and have found the other vessels still waiting for more favourable 

 weather. With respect to condensation in marine engines it is almost 

 invariably effected by surface-condensers, and thus it is that the boilers, 

 instead of being fed with salt water as they used to be, involving 

 continuous blowing-off and frequently the salting-up of the boiler, 

 are now fed with distilled water. It should be noticed, however, 

 that in some instances, owing to the absence of a thin protecting scale 

 upon the tubes and plates, very considerable corrosion has taken place, 

 especially where distilled water, derived from condensers having un-tinucd 

 brass tubes, has been used for the feed, and where the water has carried 

 into the boiler fat-acids arising from the decomposition of the grease 

 used in the engine ; means are now employed by which these effects are 

 counteracted. 



I wish before quitting this section of my subject, to call your 

 attention to two very interesting but very differing kinds of marine 

 engines. One is the high-speed torpedo-vessel or steam launch of which 

 Messrs. Thornycroft have furnished so many examples. In these, owing 

 to the rate at which the piston runs, to the initial pressure (120 lbs.), and 

 to very great skill in the design, Messrs. Thornycroft have succeeded in 

 obtaining a gross indicated horse-power for as small a weight as half a 

 cwt., including the boiler, the water in the boiler, the engine, the pro- 

 peller shaft, and the propeller itself. To obtain the needed steam from 

 the small and light boiler, recourse has to be made to a fan-blast driving 

 air into a closed stoke-hold. From the use of a blast in this way two 

 excellent things happen : one is, as already stated, that from a small 

 boiler a very large amount of steam is produced, and the other that the 

 artificial blast, wlien thus applied, is unaccompanied by the dangers which 

 arise when, under ordinary circumstances, the blast is applied only to 



