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XL. A Method of determining the specific Heat of Bodies from 
their Expansion. By Mr. Tuomas Trepcotp. 
To Mr, Tilloch. 
Sir, — Tus properties of matter are generally divided into two. 
classes, that have been termed Mechanical and Chemical: and 
however important the connexion between these properties may 
be, they have not been compared with that attention which the 
progress of science appears to require. Perhaps the distinction 
of science into Mechanical and Chemical is not favourable to such 
comparisons; and on that account it would be well if it were less 
marked than it is. The distinction has, however, heen gradually 
lessening, and it is to be hoped will soon disappear altogether ; 
for, in as far as they can be considered as sciences, they are founded 
on the same principles. In both departments it must be grati- 
fying to every lover of science to find so many points determined 
by independent experiments, which serve as land-marks to keep 
theoretical inquiry within its proper limits. 
In every inquiry respecting the properties of bodies it is de~ 
sirable to show the dependence of these properties upon one an- 
other; indeed it is evident that the essential distinctions of the 
elementary particles of matter are few, notwithstanding its ap- 
parent diversity of forms and properties; consequently these 
forms and properties must be dependent on one another, 
At present I will attempt to show that the specific heat of 
bodies may be derived from their expansion. But, as I may as- 
sume as axioms some properties of heat that are not fully esta- 
blished, it will be preferable to state them.—I consider heat to 
be a real substance, possessing weight, magnitude, attraction, 
&c. but its specific weight so small that it eannot be determined 
by our instruments. Also, that when heat is added to another 
body, unless it causes a change of state in the body to. which it 
is added, it does not combine, but the compound remains what 
may be termed a mechanical mixture. 
Let m be the magnitude of any body; and S the weight of a. 
cube of the same body whose side is unity. Also, let A be any 
magnitude of heat. Then the magnitude of the body added to 
that of the heat will be =m-+h; and let S’ be the weight of 
a cube of the compound, the side of which is unity. Then, be- 
cause the weight of the heat is. insensible; (m+h) S=mS; 
and the expansion is equal to the bulk of heat added, 
o__c/ 
Hence a ~ =h= the magnitude of the heat when the 
specific weights are known. 
And “°_ — $’= the specific weight of the expanded body. 
meh 
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