THE KINEMATICS OF MACHINERY. 



107 



of the elements 2 and 3, is equal to the radius of the disc a. 

 With the mechanism in the form shown in Fig. 21 some 

 separate means has to be provided for keeping 6 against a 

 when the latter is moving upwards. 



Fig. 22 is another rotary engine, which has been patented 

 a dozen times since its first invention in 1 805. It is based 

 upon the mechanism of Fig. 16 (C" 3 P-*-)*. The fixed 

 link a is here made the steam cylinder, while d becomes a 



Fia. 21. 



moving piston. The reference letters are the same as before. 

 It will be noticed that the cylindric element of the link c is 

 expanded to include its prismatic element ; in all the cases 

 formerly noticed the latter had been the larger. 



In order to illustrate this part of his subject Reuleaux 

 examines (in the work I have already mentioned) some forty 

 or fifty rotary engines and pumps all derived form the (G" 4 ) 

 chain and such modifications of it as we have been looking 



