CONTINUOUS hait.way brakes. 



177 



"p to tJio instant of application of tlio brakes, had been 

 inaintainod on both sides of a moving piston— or, in some 

 instances, a fixed one, where a movable cylinder is carried 

 on each vehicle, and is connected with the levers carrying 

 the brake blocks. The destrnction of the 0(iuilibrlnm which 

 maintained the piston at rest and the brakes " off," is 

 brought about by altering the above-named conditions of 

 pressure or of vacuum on one side of the piston, whence 

 motion of the piston or cylinder ensues — according as it is 

 the former or latter which is movable, and connected with 

 the brake rigging. 



The part of the mechanism which transmits the available 

 power from the point where it is applied to the point whore 

 it is utilized, — usually termed the " brake rigging," — is much 

 the same in all continuous brakes, and needs no particular 

 description. 



To many, the abstract just given of the " classification 

 "t continuous brakes" may appear meagrfl, and of too 

 theoretical a nature ; this arises from the fact that whore 

 a classification of mechanisms is based upon " pn-inciples," 

 and not upon details of construction, the ground covered 

 or affected by these principles cannot bo exactly defined. 

 •New inventions may appear, which may be further mani- 

 lestations of particular principles ; therefore, unless wo are 

 to bo constantly roconstnicting old. classifications, or de- 

 vising now ones, we must state " principles " in such general 

 terms as to afford grounds for believing that the classifi- 

 cation of mechanisms in which they exist may be broad 

 finough to include inventions that have been and inventions 

 that may yet be made. The number of "principles" to 

 bo found are fewer than the number of applications of them 

 which may be made. 



What a gonoral " classification " of mechanisms lacks, 



