i86 OUR PHYSICAL WORLD 



in the steam intake, which is thereby closed as the collar rises: 

 When the engine slows down, the balls move in closer to the 

 vertical rod, the collar is pushed down, and the valve is opened. 

 In this way the engine is made to run at a nearly uniform speed. 



The exhaust steam is made to heat the water before it is sent 

 into the boiler until it is almost ready to boil. Since the pressure 

 in the boiler is great the water has to be driven in by force. An 

 injector is generally used for this purpose. 



The stationary engine came rapidly into use late in the eight- 

 eenth and early in the nineteenth century, for running machines 

 that were being invented to aid man in his labors. Up to this 

 time manufacture had been largely a household process. The 

 shoemaker made the shoes at home and his wife and children 

 all helped. Wool was combed, corded, spun into thread, dyed, 

 and woven into cloth, all in the home. The spinning-wheel 

 and hand-power loom were part of the necessary equipment in 

 the home of the weaver and everybody worked, including father. 

 On the farm everything was done by hand (Figs. 74, 75). In 

 town and country it took the combined labor of all the family to 

 pay for the necessary food, clothing, and shelter. Even the little 

 children found some tasks. But the steam engine and power 

 machinery began to shift manufacture from the home to the 

 factory. Workmen saw machines doing the work of 100 hand 

 operatives (Fig. 76, p. 188). They were afraid the factories were 

 going to deprive them of the chance to work, for children and 

 women could tend machines. Mobs tried to burn the mills and 

 destroy the machines and in many cases they succeeded. But 

 what appeared temporarily as a menace to labor proved a great 

 blessing, for steam power and machinery increased production. 

 A single steam engine can do the work of 10,000 men, and do it 

 ceaselessly and tirelessly. 



The more expeditiously man can obtain raw materials, like 

 iron, coal, wood, grain, and manufacture them into the things 

 he needs, the more rapidly he accumulates wealth. William E. 

 Gladstone once estimated that the wealth of the world increased 



