THE CONQUEST OF TIME AND SPACE 



created another. The second one was the problem of 

 how to stop the trains once they had started. On short 

 trains made up of the light cars used at first, the hand 

 brakes were sufficiently effective for practical purposes. 

 But as trains were increased in length and weight and 

 were run at high speeds, it became imperative to find 

 some means of stopping such trains quickly and with 

 certainty. 



With a hand brake working on each pair of trucks, 

 as on passenger coaches, it was possible to make rea- 

 sonably quick stops when there were enough members 

 of the train crew to work all the brakes simultaneously. 

 But in practice it was found impossible to maintain 

 this ideal condition. For emergency stops the brake- 

 men were summoned by signals of the whistle given by 

 the engineer, and there was necessarily some little in- 

 terval of time after this signal before the most alert 

 crew could begin the relatively slow process of apply- 

 ing the brakes. 



The engineer himself could give valuable aid in 

 stopping the train by reversing his engine, the locomo- 

 tive acting as a brake to check the oncoming cars. But 

 this check acted only at the forward part of the train, 

 and being applied suddenly, caused the rear cars to 

 rush against the forward cars with terrific force, some- 

 times driving in the bumpers and wrecking the train. 

 Obviously an ideal system of brakes must be one that 

 acted upon all the cars of the train simultaneously and 

 under control of the engineer; and presently such a 

 system was invented by Mr. George Westinghouse. 



Other inventors had tried to produce a practical 



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