156 



The Earl of Berkeley and Dr. Burton 



on a 



couple. The rotation of the weight-carrier is communicated 

 to the piston in much the same way, except that the equality 

 between the constituents of the driving couple depends, in 



Fig. 2. 



Fiff. 3. 



this case, on the approximately equal flexibility oE two flat 

 springs F F attached to the piston-head, and engaging with, 

 pins H H as indicated in the upper part of fig. 2. 



Description of joints. — The various tees, elbows, and ex- 

 tensions (there are some 40 joints in all) used in this- 



