FIFTY YEARS OF MECHANICAL ENGINEERING. 533 



a short time ago had been left to sailing-vessels. This steamship has 

 some points of interest, and illustrates the most advanced ideas on 

 steam-engineering as applied to the mercantile marine. The engines 

 of this steamer are triple expansive, having one high-pressure, one in- 

 termediate, and one low-pressure cylinder, using steam at 125 pounds 

 pressure, generated by boilers whose only peculiarity consists in the 

 fact that they are capable of withstanding such a pressure. On trial 

 these engines gave one horse-power for 1'28 pound of coal burned 

 per hour. This would, according to the usual analogy, indicate a 

 daily working efficiency of about 1*50 pound to the one horse-power. 

 This steamer can carry coal for a voyage of 12,000 miles, and, with 

 proper use of sails, could probably keep under steam for two months 

 without coaling. The weight of the engine and boilers of 1832 was 

 about 1,000 pounds to the horse-power ; to-day it is about 300, and 

 in some instances has been reduced to forty-five pounds to the horse 

 power. 



An English firm have recently completed a small light compound 

 engine, which, in point of weight, eclipses anything heretofore built. 

 This engine is made of steel and phosphor-bronze ; all parts are built as 

 light as possible, the rods and shafting and all parts possible being bored 

 out to reduce weight. At a speed of only 300 revolutions a minute 

 they indicate over twenty horse-power, and weigh but 105 pounds all 

 told. This engine would give fully thirty horse-power actual at a 

 piston-speed of 500 feet a minute. The size is three and three quar- 

 ters high pressure, seven and a half low pressure, and five stroke. That 

 thirty horse-power can be had from a proper utilization of steam and 

 proper distribution of 105 pounds of metal is certainly most astonish- 

 ing, especially so, considering that the engine is compound. A ship of 

 2,500 tons displacement was almost unknown fifty years ago ; to-day 

 the transatlantic steamer, the highest class of the mercantile marine, 

 has from 8,000 to 13,500 tons displacement, and engines of 5,000 to 

 10,000 one horse-power. Several of the transatlantic liners have shown 

 a mean ocean-speed of twenty miles an hour, and make the passage in 

 less than seven days. 



The present generation has grown so accustomed to the results of 

 the progress of mechanical science that it has long ceased to wonder 

 at its greatest works. 



It may be well here to speak of the torpedo-boats which have been 

 recently built for the English Government ; they indicate the extreme 

 limit of naval construction of this day. These little instruments of 

 destruction are only eighty-seven feet in length, ten and a half feet in 

 beam, forward draught eighteen inches, aft fifty-two inches, total dis- 

 placement thirty-three tons. The engines are compound condensing, 

 of the intermediate receiver type, high-pressure cylinder twelve and 

 three fourths inches, low-pressure twenty and three fourths, stroke 

 twelve inches, and indicated over 500 horse-power, with a gross weight 



