614 On the Materiality of Caloric. 
trable, since if it could exist, at the same time, 
in the same place, with other bodies, their vo- 
lume would never be enlarged by the addition 
of heat. Of form or figure, as only a mode of 
extension, it is unnecessary to prove that caloric 
is possessed ; and indeed there is perhaps only 
one general quality of matter, that will not be 
allowed it, viz. attraction. That caloric is in~ 
fluenced by the attraction of gravitation, or by 
cohesive attraction, has never yet been proved. 
Yet the various experiments of Buffon, White- 
hurst, Fordyce, Pictet, &c. cannot be alleged 
as proofs, that it is actually devoid of this pro- 
perty; since they only decide, that the small 
quantities, which can be artificially collected, 
aré not to be set in the ballance against the 
grosser kinds of matter. One kind of attraction, 
that which has lately been termed chemical affiv 
nity, may, I think, after a full survey of pheno- 
mena, be fairly predicated of caloric—and if its 
possession of this quality be rendered probable, 
we shall thence derive a powerful argument, in 
favour of its materiality. 
That chemical affinity has a considerable share 
ii producing thé phenomena of heat, appears 
probable from the following considerations. 
i. All the characters, distinguishing caloric 
when separate, ceasé to be apparent, when it 
has contributed to a change of form in other 
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