868 A short Account of some Discoveries 
spiration of animals, the growth of plants, and various 
_other phenomena in nature, may be so many effects pro- 
duced by the same universal cause; and this cause may oc- 
casion the particles of matter to act upon one another so as 
to produce all the various changes which constitute the 
science of chemistry. f 
If the nature of combustion was clearly understood, the 
philosophy of chemistry might then be erected upon a solid 
foundation, But this grand operation of nature still re- 
mains unexplained in a clear and satisfactory manner, not- 
withstanding the various hypotheses that have been in- 
» vented by the most learned philosophers. 
Those who first attempted to explain the phenomena of 
combustion, supposed that a certain elementary body 
called fire existed:in matter, which possessed the property 
of devouring certain other bodies. 
Other theories have since been founded on different 
principles ; as, 
1. On the ether of Sir Isaac Newton.—2. On the spirit 
of saltpetre of Dr. Hook.—3. On the phlogiston of Stahl, 
—4, On the Jatent heat of Dr. Black.—And Sthly, Lavoi- 
sier founded a theory upon the absorption of oxygen hy a 
combustible body. 
*¢ But at present, in consequence of the recent and un- 
expected Galvanic discoveries, the Lavoisierian theory stands 
a considerable chance of being new modelled, if not in 2 
‘great measure overthrown. Several important and neces 
sary modifications have already taken place, and others not 
Jess important will probably follow *.” 
Sir Humphry Davy supposes, that the phenomena of 
heat consist of a vibratory motion of the particles of heated 
bodies f. 
But as we are not informed what force or power acts 
upon the particles of matter, to put them into a vibratory 
-motion, this hypothesis seems to be as inconclusive as any 
of the preceding. 
There is, however, a great number of chemical effects 
which are produced by the same cause ; and as combustion 
is one of them, this cause, therefore, is an interesting sub- 
ject of inquiry. 
When a Leyden jar is charged it contains two invisible 
fluids, one on the inside and the other on the outside ; and 
as these fluids are of such a nature as to produce no effect 
* Edinburgh Ency. vol. vi. page 8. 
+ Davy’s Elements of Chemical Philosophy, p. 9% 
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