LOCOMOTION BY RIVER AND RAILWAY. 



10. It is not only in dimensions that these vessels have under- 

 gone improvements. The exhibition of the beautifully finished 

 machinery of the English Atlantic steamers did not fail to excite 

 the emulation of the American engineers and steam-boat pro- 

 prietors, who ceased to be content with the comparatively rude 

 though efficient structure of the mechanism of their steam-boats. 

 All the vessels more recently constructed are accordingly finished 

 and even decorated in the most luxurious manner. In respect of 

 the accommodations which they afford to passengers, no water- 

 communication in any country in the world can compare with 

 them. Nothing can exceed the splendour and luxury of the fur- 

 niture. Silk, velvet, and the most expensive carpeting, mirrors 

 of immense magnitude, gilding and carving, are used profusely in 

 their decorations. Even the engine-room in some of them is lined 

 with mirrors. In the Alida, for example, the end of the room 

 containing the engine is composed of one large mirror, in which 

 the movements of the highly-finished machinery are reflected. 



11. The new and largest class of steamers are capable of 

 running from twenty to twenty-two miles an hour, and make, on 

 an average, eighteen miles an hour. These extraordinary speeds 

 are obtained usually by rendering the boilers capable of carrying 

 steam from forty to fifty pounds pressure above the atmosphere, 

 and by urging the fires with fanners, worked by an independent 

 engine, by which the furnaces can be forced to any desired extent. 



It is right to observe here that this extreme increase of speed is 

 obtained at a disproportionately increased consumption of fuel. 

 When the speed is increased, the space through which the vessel 

 must be propelled per minute is increased in the same proportion : 

 and, at the same time, the resistance which the moving power has 

 to overcome is augmented in the proportion of the square of the 

 speed. Hence, the effect to be produced by the moving power per 

 minute, is increased by two causes: first, the actual resistance 

 which it has to overcome is augmented in the ratio of the square 

 of the speed ; and, secondly, the space through which the moving 

 power has to act against this resistance in each minute is 

 increased in the ratio of the speed. Thus, the total expenditure 

 of moving power per minute will be augmented in the proportion 

 of the cube of the speed. 



Let us suppose the speed to be increased, for example, from 

 eighteen to twenty-one miles an hour : the power to be expended 

 per minute to produce this effect must be increased in the ratio of 

 the cube of 18 to the cube of 21 ; or, what is the same, in the ratio 

 of the cube of 6 to the cube of 7, that is, in the ratio of 216 to 

 343, or as 3 to 5 very nearly. 



Hence, if the furnaces could be worked with equal economy, an 

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