148 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Fig. 5 is from tlie same cylinder, with the cranks at 90 degrees, but 

 with the receiver enlarged from 1^% to 2y%, the volume swept bj^ the 

 high-pressure piston. 



Tig.lJEngimwofJiir^ compound Qmiksat90!' 



Jo.' 



Fig. 4 is a diagram from the same cylinder with the cranks at 90 de- 

 grees, but with the original volume of receiver, namely, ly%, the volume 

 swept by the high-pressure piston. 



The relative contours of these diagrams and their variance from the 



