Reply to a Criticism of Prof. Olmsted. 53 
to the piston of a steam engine the wonted power: or that 
the particles of air should prevent a column of mercury, al- 
most infinitely heavier, from entering any space in which 
Again, admitting it to be conceivable that the momentum 
of particles so light may be competent to such effects, it is 
utterly impossible that these could be permanently sustained ; 
since in all cases where motion is commumeated, what is 
gained by one body is lost by another: so that the motion 
of the body communicating the motion, is lessened at eve 
impact, and finally ceases.—Further, since it is self-evident 
that a body, acting directly upon another, cannot produce a 
motion greater than its own, it is incredible that heated solids 
should, by any possible movements of their particles, produce 
he prodigious velocities, which, according to the disputed 
doctrine, must be attributed to aeriform matter, when its levi- 
ty and its power of resistance, as above exemplified, are taken 
into view. zs hex Ree THER 
I must leave it to the reader to judge how far these argu- 
ments merit the oblivion, to which Prof. Olmsted would con- 
sign them, 
