34 
would thus appear at first sight that the mere presence of 
a moving body, has given us the power of obtaining work 
from an enclosure, all of whose particles were originally at 
the same temperature. This appears however to be opposed 
to the theory of the dissipation of energy, and in conse- 
quence we are induced to think there must be some error in 
the assumption. 
Now does not the unwarranted part of the hypothesis 
consist in our supposing that the revolving system can con- 
tinue to revolve without losing part of its visible motion ? 
When two moving bodies approach or recede from each 
other is it not possible that each loses a small part of its 
visible energy while at the same time there is a surface dis- 
turbance produced in both ? 
It might be said that believing in a medium pervading 
all space we were prepared for a stoppage of motion of this 
nature, and that there is therefore nothing gained by the 
supposition which has been made; but it might be replied 
that by looking at the problem in the above light we appear 
to connect this stoppage of motion with other facts, besides 
beino- made aware of a source of surface disturbance when 
O 
cosmical bodies approach or recede from each other. 
Postscript added 19th November. — If we imagine a stop- 
page of the motion of cosmical bodies of the nature above 
described, then if the two approaching bodies be exactly 
equal and similar, either extremity of the medium between 
them will be similarly affected by the motion derived from 
the approaching bodies; but if these bodies are unequal, the 
two extremities of the medium will be dissimilarly, affected. 
