406 



REPORT 1872. 



because C D' (equal 2\ inches) is one half of the length of the rod Q. The 

 " quantity " of motion in going along D' to A' would, however, have been the 

 same as it was in passing from D to A, because D' A' equals D A ; but an 



Fig. 4. 



Fig. 5. 



.M 



equal " quantity " into half the " rate " will only give half the total amount, 

 aud therefore the wheels R would have recorded a half revolution, equal 5 

 square inches, thus accurately giving the ai'ea C J)', A' E. On the other hand. 



