on some of the leading Doctrines of Caloric, Sc. 39 
basis ; leaving to his pupils, the subordinate task of investigating 
their individual applications. Hence, the elastic forces of the 
vapours, arising from different bodies, at different temperatures, 
seem to have occupied him very little, if at all. This subject was 
examined, however, with great ability, by two of his most di- 
stingnished friends, Professor Robison and Mr. Watt. The in- 
vestigations of the former were published in the Encyclopedia 
Britannica, article Steam; while we have still to regret our ig- 
norance of those executed by the latter philosopher, with pro- 
bably a more complete apparatus, and more extensive views. We 
are indebted to him, indeed, for some curious observations on the 
latent heat of steam, at different temperatures, which make us 
lament more, the want of those on the elastic forces themselves. 
Mr. Dalton, whose peculiar speculations on caloric and me- 
teorology led him to study the formation and variable elasticity of 
vapour with great attention, has since then favoured the world 
with many excellent dissertations, and is now reckoned the first 
authority on the subject. Mr. Dalton’s experiments on the 
steam of water were carried no higher than its ordinary boiling 
point ; but from the observed progression of its elastic force he 
investigated a formula, and calculated from it a table for the 
higher temperatures”. 
in the second number of the Journal Polytechnique, M. Be- 
tancourt, an eminent Spanish engineer, long resident at Paris, 
published a set of experiments on the same subject, the results 
of which différ from those of Mr. Dalton in many particulars, 
but most remarkably in the higher part of the scale. 
Having had my mind often called to this important inquiry in 
the course of my public lectures on the applications of Science to 
the Arts, an apparatus of a very simple nature occurred to me, 
about two years ago, by which I hoped to be able to determine, 
with great precision, the elastic forces of vapours at any tempe- 
rature, from zero of Fahrenheit toa much higher degree of heat 
than even Betancourt seems to have reached. The experiments 
were made soon after that time, but circumstances have till now 
prevented me from at ranging them for publication. 
With Betancourt’s apparatus I am not acquainted, having seen 
only the brief table of results, inserted in our systematical works 
on chemistry. Professor Robison’s consisted of a strong boiler 
or digester, containing the water, and furnished with three small 
apertures ; the first receiving the bull of a thermometer, the se- 
cond covered with a safety-valve, and the third having a baro- 
meter tube attached, At first I used a similar construction 3 but 
finding it hazardous, and somewhat unmanageable in the high 
* Manchester Memoirs, vol. v. p- 563. 
heats, 
