. Revised and enlarged ed. of the science of railways . Earlv Lever Brake. 1630. 292 RAILWAY EQUIPMENT. as either of these. Some of them are illustratedherewith. Among these crude devices may be mentionedthe Le Caan brake, so-called. This was oper-ated by dropping the lever. When this was donethe shoe of the brake, falling to the ground,formed a wedge, thus retarding the revolution of the wheel. Among otherprimitive make-shifts there werevarious forms ofchain brake, andlater the deviceswhich steam m was used; also,the hydraulicbrake, operatedby liquids storedunder high a hig
. Revised and enlarged ed. of the science of railways . Earlv Lever Brake. 1630. 292 RAILWAY EQUIPMENT. as either of these. Some of them are illustratedherewith. Among these crude devices may be mentionedthe Le Caan brake, so-called. This was oper-ated by dropping the lever. When this was donethe shoe of the brake, falling to the ground,formed a wedge, thus retarding the revolution of the wheel. Among otherprimitive make-shifts there werevarious forms ofchain brake, andlater the deviceswhich steam m was used; also,the hydraulicbrake, operatedby liquids storedunder high a higher grade, comes the so-calledplain vacuum brake, operated by an ejector,whichwithdraws the air from the pipes, thereby pro-ducing a vacuum more or less perfect. Then the automatic vacuum brake, operatedby the application of air at atmospheric pressureto a vacuum cylinder. Also the compressed air brake, worked by ahair pump, forcing air into the pipes, the air beingstored in a reservoir under the vehicle. Still other forms and modifications might be. New-Castle-on-Tyne. 1630. THE AIR BRAKE. 293 enumerated, but those given are suflBcient to rep-resent, substantialh% the progressive steps in theevolution of the brake, and direct attention tothe practices observed and the principles in-volved. Among the writings of the ancients we findmention of the use of the brake, coupled withvague references to the principles governing , however, definite. Indeed, there waslittle use for such a device in connection withthe chariots andrude carts andwagons used inthe primitiveages of theworld. For along period theaxle and wheelwere one andrevolved in uni-son. Such wasthe primitive cart. When this was the case there couldbeen little need of tliQ friction afforded
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