196 On some of the leading Doctrines of Caloric, ec. 
density, and latent heat of different vapours, harmonize with 
chemical phenomena in general, I leave to others to determine.’ 
It certainly agrees with that unaccountable fact. Whatever be 
the fate of the investigation of the general law now respectfully 
offered, the statement of Mr. Watt may be implicitly received 
under the sanction of his acknowledged sagacity and candour. 
Conclusion.—To the theory of latent heat, which, like the hy- 
drostatic paradox of Archimedes, might have remained for ages 
a barren, though beautiful proposition, the fertile genius of that 
philosopher gave all at once its noblest application, and most be- 
neficial influence on human life, by his new steam-engine. After 
him, many minds of the first order for science and ingenuity have 
offered schemes of further improvement ; but all either frivolous 
or abortive; with such prophetic judgement had Mr. Watt anti- 
cipated the happiest form and structure of which it was suscep- 
tible. 
Under this conviction, it is with much deference that I draw 
the following practical inferences from the last train of experi- 
ments. 
Since the vapour of alcohol, having the same elastic force as 
the atmosphere, contains ,,4, of the latent heat of ordinarysteam, 
and since its elastic force is doubled at the 206th degree (6° be- 
low the boiling heat of water), with perhaps + of additional ca- 
loric ; might we not, in particular circumstances, employ this 
vapour for impelling the piston of a steam engine? The con- 
densing apparatus could, | imagine, be so constructed, as to pre- 
vent any material loss of the liquid, while more than a quadruple 
power would be obtained from the same size of cylinder at 212°, 
with an expenditure of fuel not amounting to one half of what 
aqueous vapour consumes; or the power and fuel would be as 
3 to 1, calling their relation in ordinary steam | to 1. A con- 
siderable engine could thus also be brought within a very mo- 
derate compass. Possibly, after a few operations of the air- 
pump, the incondensable gas may be so effectually withdrawn, 
that we might be permitted to detach this mechanism, which, 
though essential to common engines, takes away one-fourth of 
their power. In a distillery in this country, or on a sugar estate 
in the colonies, a trial of this plan might perhaps be made with 
advantage. While exercising its mechanical functions of grind- 
ing, mashing or squeezing the canes, it would be converting or- 
dinary into strong spirit for rectification, or for the convenience 
of carriage. Might not such an engine be executed on a small 
scale, for many purposes of domestic drudgery? It would un- 
questionably furnish a beautiful illustration in philosophy, to 
make one small portion of liquid, by the agency of fire, imitate 
the ceaseless circulation and restless activity of life. 
XXX. On 
