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been used for the haulage of heavy, loads in mining districts, and 

 George Stephenson strongly advocated the employment of steam- 

 power for this pm-pose. The success of Stephenson's engine, the 

 "Eocket," in the competition trial of steam locomotiTes on the 

 Manchester and Liverpool Railroad, in 1829, settled the question of 

 the employment of steam power, not only for hauling heavy goods, 

 but also for the transport of passengers. The application of the 

 steam engine to ships was commenced very early in the present 

 century. The crossing of the Atlantic by steamers was inaugurated 

 by the voyage of the Great Western in 1838 ; the time occupied was 

 15 days. We are now able to cross in about 7^ days. The screw has 

 now entirely superseded the paddle, as a propeller for ocean-going 

 merchant steamers, as well as for men-of-war. Several types of 

 the marine engine have been introduced for driving the screw 

 propeller, differing considerably in the arrangements of their parts ; 

 but they are all modifications of the double-acting, condensing, 

 rotative engine. The pressure of steam used has gradually increased, 

 and the system of using steam "expansively" has been carried out 

 more completely, with a corresponding advance in economy of fuel. 

 In good marine engines, at present, the work of a strong horse for 

 an hour is obtained for 21b8. of coal, costing less than a farthing. 

 The important part played by steam, in the economy of the most 

 recent men-of-war, was then alluded to. The propulsion and 

 steering of the ship, the loading and handling of the guns, the 

 revolving of the turrets, the raising and charging of the torpedoes, 

 &c., are all dependent upon steam power. Steam is also used to 

 supply the ships with air, with fresh water, and with the electric 

 light ; steam pumps are fitted for a great variety of pui-poses ; and the 

 large engines which propel the ships are themselves controlled by 

 little steam engines so easily that the reversal, from full speed ahead 

 to full speed astern, occupies only a few seconds. The Lecturer next 

 passed on to inquire respecting the source of the power exerted by 

 the steam engine. After showing that a power of doing work, or 

 " energy," exists in the universe in various forms, and from various 

 causes, he then explained that heat is one of the forms in which 

 energy can exhibit itself. The energy which appears in the foim 

 of heat when coal is bunied, came originally from the sun. Coal is 



