In the first air brake invented by George Westinghouse, the locomotive was provided with a reservoir in which air was stored and compressed by means of a steam-operated air pump. The cars were each provided with a cylinder and piston connected to the air reservoir through a valve conveniently located in the engineer’s cab. The piston of the air cylinder was connected with the air brakes so that whenever the engineer wished to stop his train he merely turned on the compressed air and all the brakes in the train were operated. This was a great saving over the previous system of providing brakemen to operate hand brakes. Unfortunately, the problem of stopping a train was not as simple as all this. On a long train the cylinders near the engine were the first to receive pressure sufficient to operate the brakes, and as a result, the forward part of the train was retarded more than the rear part at the start of the brake operation, and the train came to a stop with a series of jolts. Another serious disadvantage was the fact that an enormous reservoir was required to furnish all the air necessary for a long train. But the most serious drawback was the fact that occasionally a train broke apart and then the engineer was powerless to control the brakes of the detached portion of the train. If the accident occurred on a down grade, there would result a collision between the cars running by their own momentum and gravity and those attached to the engine. This led to the present system of reversing the process which consists in keeping air pressure constantly in the train pipe and setting the brakes by relieving the pressure in the train pipe.