52 Reply to a Criticism of Prof. Olmsted. 
been so dull as to consider a disproval of the hypothesis of Sis. 
- Davy as establishing that which I have myself espoused ; 
and that I had advanced no direct arguments in favour of the 
materiality of heat, although to such arguments, the latter 
part of the essay is devoted. I beg leave here to quote the 
reasoning, as I am still of opinion that it is unanswerable, 
notwithstanding the unaccountable neglect with which it has 
been treated by the professor. —_- 
“ We see the same matter, at different times, rendered self- 
attractive or self-repellent ; now cohering in the solid form with ~ 
e 
self-repellent and self-attractive ?. Suppose them to be so—one of 
e two properties must predominate ; and in that case, we should 
not perceive the existence of the other. It would be useless, and 
the particles would, in effect, sess the predominant property 
alone, whether attraction or repulsion. If the properties were 
equal in power, they would annihilate each other, and the matter 
would be, as if void of either property. ‘Chere must, therefore, 
be a matter ia which the self-repellent power resides, as well as 
matter in which attraction resides.” 
Tn support of my opinion, I also cited the radiation of heat 
in vacuo, agreeably to an experiment of Sir H. Day y himself, 
cause of it be not material. 
I did not dwell on this fact, because I supposed its impor-~ 
tance generally known and admitted, and conceived that 
it would produce the most forcible impression, when viewed 
in its greatest simplicity. 
In opposition to Davy’s hypothesis, I had advanced several 
arguments, of which Prof. Olmsted notices but-one. With 
frespect to that, it does not appear to me that he has adduced 
any fact, or any learning, which can invalidate the applica- 
uon, which I have made of a rule admitted by him to be true 
to a limited extent. It is enough for me, if the case in point 
