THE GROWTH OF THE STEAM-ENGINE. 



141 



rotary motions, .and temporarily adopted that known as the " sun-and- 

 planet wheels," subsequently using the crank. 



The adaptation of the steam-engine to the production of rotary 

 motion was soon succeeded by the introduction of the Double-Act- 

 ing Engine, the Fly-ball Governor, the Counter, the Steam-Engine 

 Indicator, and other minor but valuable improvements, which were 

 the final steps by which the Watt steam-engine became applicable to 

 driving mills, to use on railroads, to steam-navigation, and to the 

 countless purposes by which it has become, as it has already been de- 

 nominated, the great material agent of civilization. 



40. Fig. 16 represents the Watt Double-Acting engine. It will be 

 noticed that it differs from the Single- Acting engine in having steam- 

 valves, B B, and exhaust-valves, E E, at each end of the cylinder, 

 thus enabling the steam to act on each side of the piston alternately, 

 and practically doubling the power of the engine. 



The end of the beam opposite to the cylinder is usually connected 

 with a crank-shaft. 



Watt's Workshop at Home. 



41. At this point, the history of the steam-engine becomes the 

 story of its applications in several different directions, the most im- 

 portant of which are the raising of water, which has hitherto been its 

 only application ; the propulsion of carriages, as in the locomotive- 

 the driving of mills and machinery ; and steam-navigation. 



engine ; 



