Dr. Hare's reply to Professor Olmsted. 9 



agreeable to the laws of motion, make that hypotheses un- 

 duly " wear a mechanical aspect" or subject it to an applica- 

 tion of principles " which have no bearing on it whatever £" 



In his first critique, the author alleged Davy's reasonings 

 to be " idle" because they were " mechanical" In the critique 

 before us, I am condemned for treating them as " mechan- 

 ical." 



A sufficient answer to this objection, was afforded in my 

 essay in the following language : 



" It may be said that this motion is not measurable upon me- 

 chanical principles. How then I ask, does it produce mechani- 

 cal effects ? These must be produced by the force of the vibra- 

 tions, which are by the hypothesis mechanical : for whatever; 

 laws hold good in relation to moving matter in mass, must ope- 

 rate in regard to each particle of that matter. The effect of 

 the former, can only be a multiple of that of the latter. Indeed 

 one of Sir Humphrey Davy's reasons for attributing heat to cor- 

 puscular vibration, is, that mechanical attrition generates it. 

 Surely then a motion produced by mechanical means, and which 

 produces mechanical effects, may be estimated on mechanical 

 principles." See Vol. IV, page 144 of this Journal. 

 » " In the hypothesis, (says Professor Olmsted,) the motions sup- 

 posed, are .those which occur between particles of matter, and 

 at insensible distances. In the refutation, the principles applied 

 are such as belong to those motions which occur between masses 

 of matter, and at sensible distances." 



The laws which regulate the production, or transfer, of 

 motion, being established as respects any given mass, or 

 quantity, can the division of it into two parts, ten parts, or 

 a million parts, or into any possible number of parts, or par- 

 ticles, render those laws inapplicable ? The same argument 

 may be opposed to his distinction between sensible and in- 

 sensible distances, as if a law could cease to operate in con- 

 sequence of the spaces being too small for our vision ! ! ! 



Since a whole can be no more than a multiple of its parts, 

 a law cannot be true of motion, in any given distance, which 

 does not hold good with respect to any part of that distance. 



The minuteness of the distances within which movements 

 can take place, in solids, is cited by me, as a potent objection 

 to ascribing to intestine motion the expansive power impar- 

 ted by them, when heated, to vaporizable substances, as in 

 the case of water converted into steam by hot iron ; but if 

 such phenomena do result from intestine motion, and if the 

 transfer of expansive power, be a transfer of such motion, 



Vol. XIII.— No. 1. 2 



