Dr. Hare's reply to Professor Olmsted. 1 1 



tion has this effect, by generating a centrifugal force ; but it 

 cannot be imagined that in every mass, expanded by heat, 

 the particles, by revolving about a common center of gravi- 

 ty, generate a centrifugal force which, counteracts cohesive 

 attraction ; and thus, enables them to exist at a greater dis- 

 tance from each other. 



When by the affusion of hot water upon mercury, the tem- 

 perature of the latter is raised, how can the velocity of the 

 vibrations in which temperature consists, according to the 

 hypothesis, be increased in the last mentioned liquid, without 

 collision between the mercurial and aqueous atoms ? While 

 they remain asunder, the particles can have no influence upon 

 each other, unless through the medium of some inherent 

 property of attraction, or repulsion. Of the former, motion 

 is the opponent, of the latter the substitute, by the premises. 



If motion be not productive of a collision among the parti- 

 cles, in what way can it enable them to sustain that remote- 

 ness, in their respective situations, which expansion requires ? 

 It cannot be supposed that they will become either recipro- 

 cally repulsive, or less susceptible of cohesive attraction, 

 merely in consequence of their undergoing a vibratory move- 

 ment. 



Professor Olmsted had evidently a very imperfect recollec- 

 tion of the design, or execution of my essay, when he wrote 

 his critique ; or. he could not have denounced it as idly em- 

 ploying, in chemistry, those mechanical reasonings which it 

 was intended to explode. In the last number of the Journal, 

 1 devoted a page to the exposure of his error, in speaking of 

 my essay as intended to prove the materiality of heat, al- 

 though described as remarks made in opposition to Davy's 

 hypothesis. In the article now under consideration, he re- 

 peats this error in the following words : 



" In the year 1822, Dr. Hare published an essay aiming 1 to 

 prove that caloric, or the cause of heat, is a material fluid." 



I never wrote an essay of which this is a correct descrip- 

 tion. It did not appear to me expedient to recapitulate all 

 the various well known arguments in favor of a material 

 cause of calorific repulsion. To explain the phenomena of 

 heat, but two hypotheses had been suggested, one ascribing 

 them to caloric, the other to motion. The object of my essay 

 was mainly to shew, that motion could not be the cause of 

 heat, and I only incidentally introduced some direct argu- 

 ments in favor of a material cause. 



