692 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1913. 



fitted as separate auxiliary engines, instead of being driven from 

 the crossheads. Attention has been directed to devising means of 

 balancing the engines in order to reduce vibration troubles. The 

 first attempt to solve the problem of balancing was made by Messrs. 

 Yarrow, and the method known as the Yarrow-Schlick-Tweedy sys- 

 tem is now adopted in most engines of the four-crank type. This 

 method consists in arranging the relative positions of the various 

 reciprocating and revolving masses by adjusting the angles between 

 the cranks so that the inertia effects are reduced to a minimum. 

 Reduction in fuel consumption has been obtained by the collective 

 effect of a number of small savings ; by the improved condenser and 

 air pump; by the utilization of the auxiliary exhaust for feed heat- 

 ing ; and by heat economy in various ways. 



In the constant endeavor to provide greater intensity in powdi* pro- 

 duction, increase in piston speed and rate of revolution has been 

 achieved through experience in design and a better quality of mate- 

 rial and workmanship; but where conditions of exceptional power, 

 or lightness per unit of power, or both of these, have to be considered, 

 the limitations of the reciprocating type of engine become apparent. 

 In addition to the difficulties of construction and management of 

 very large units, the reciprocating engine had, as already remarked, 

 reached a point where further improvement in steam consumption 

 was not easily attained, while further reduction in weight involved 

 increase in speed of rotation, with its attendant difficulties. Thus the 

 introduction of the steam turbine proved opportune, by providing a 

 way to further progress in economy, lightness, and the construction 

 of very large units, while at the same time eliminating vibration 

 troubles and relieving difficulties of engine-room management. 



The turbine entered the Atlantic lists in 1905, when the Victorian 

 and Virginian, 520 feet in length, took up their stations, and in 1905 

 the 650-foot Carmania also used the new motor. 



The 700- foot mark was passed in 1906 by the building of the White 

 Star liner Adriatic, 709 feet by 75 feet by 56 feet, with twin-screw 

 quadruple-expansion engines of about 15,000 indicated horsepower. 



Her speed was but 15 knots, and she carried 460 first-class, 500 

 second-class and 1,400 third-class passengers, 2,500 tons of coal, and 

 6,500 tons of cargo. Of her total displacement, hull claimed about 

 56 per cent; machinery, 10 per cent; fuel, 8 per cent; cargo, 21 per 

 cent; passengers, stores, and water, about 5 per cent. A comparison 

 of these approximate figures with those already given for the Cam- 

 pania shows that, per annum, the Adriatic could carry twice as many 

 passengers and three and a half times as much cargo per ton of fuel 

 as the Campania. This well illustrates the cost of speed, and justi- 

 fies the enhanced rates charged to those availing themselves of the 

 faster vessels. 



