536 
and the development of latent heat in 
compression, and the necessity for its 
ze-absorption ‘in expansion (as_the ra- 
tionale of the subject is at‘present un- 
derstood) must awaken some doubts as 
to the economical results to’be obtained 
by employing the steam of water under 
very great pressures, and at very ele- 
vated temperatures. 
“No such doubts, however, can arise 
with respect to the use of such liquids, 
as require for their existence even a 
compression equal to, that of the weight 
of 30 or 40 atmospheres: and where 
common temperatures, or slight eleva- 
tions of them, aré sufficient to produce 
an immense elastic force ; and when the 
principal’ question to be discussed, is 
whether the effect of ni¢chanical motion 
is to be most easily produced by an in- 
crease or diminution of heat by artificial 
means. 
With the assistance of Mr. Faraday 
T have made some experiments on this 
subject, and the results have answered 
my most sanguine expectations. Sul- 
phuretted hydrogen, which condenses 
yeadily at 3° F., under a pressure equal 
to that which balances the elastic force 
of an atmosphere compressed to 7, bad 
its elastic force increased so as to equal 
that of an atmosphere compressed to 
by an inerease of 47° of temperature. 
Liquid muriatic acid at 3°, exerted an 
elastic force equivalent to that of an at- 
mosphere compressed to 34; by an in- 
érease of 22°, it gained an clastic force 
equivalent to that of an atmosphere 
compressed to 4, ; and by a farther ad- 
dition of 26°, an elastic force equivalent 
to that ‘of air condensed to 75 of its 
primitive volume. These experiments 
were made in thick glass tubes kerme- 
tically sealed. The degree of pressure 
was estimated by the change of volume 
of air confined by mercury in a small 
graduated gage, atid placed in a part of 
the tube exposed to the atmosphere, 
and the temperatures were diminished 
from the degree at which the gage was 
introduced, that is, the atmospheric tem- 
perature by freezing mixtures; so that 
the temperature of the air within the 
gage could not be considerably altered ; 
and as the elastic flaid surrounding the 
gage must have had a higher tempera- 
ture than the condensed fluid, the dimi- 
nution of the elastic force of the vapour 
from the fluids camnot be considered as 
overrated. 
From the immense differences be- 
tween the increase of elastic force in 
gases under high and low pressures, by 
Proceedings of Public Societies. 
(ean, 
similarincrements of temperatare, there 
can be no doubt that the denser the 
vapour, or the moré dilficuit/of conden- 
Salion the’ gas, the greater Will be its 
power under changes of temperatire as 
a mechanical agent : thus carbonic acid 
will be much more powerfal than’ mu- 
viatic acid. Th the only ‘experiinent 
which has been’ tried upon if} its’ force 
Was found to be nearly equal to thit. of 
air compressed 6° $4 at 12°R.) and ‘of 
air compressed to st at 32 degrees, 
making on inérease equal to tlie weight 
of 13 atmospheres by an’ inéréase of 20 
of temperature ; and this immense elastic 
force’ of 36 atmospheres béing exerted 
at the freezing point of Water® And 
azote, if it could be" obtained” fluid, 
would, there is po doubt; be far more 
powertal than carbonié acid; and tiy- 
drogen, in such a state, would’ exert a 
force almost incalculably’ great, and 
liable 10 immense changes’ from ‘the 
slightest variations of temperature. ~ 
To illustrate this idea, I shall qtvote 
an experiment-on alcohol of sulphur.” 
' The temperature pete Boa aeae 
raised 20 degrees above its boiling point, 
and its elastic force exansined: it was 
found equal to less than that ‘of air e6m- 
pressed to 3. It was now heated’tu'320° 
under a pressure eqttal to that of air 
condensed to 43, anda siimilar inere- 
meut of 20 degrees added’; its‘elastic 
force became equivalent:to that ‘of an 
atmosphere compressei to 392, yo) T 
I hope soon to be able to repeat these 
experiments in a more ‘minatevand! é- 
curate way; but the general-results/ap- 
pear so worthy the attention of practical 
mechanics, that Lihink ita datytodose 
no time in bringing them forward) ‘even 
in their present imperfect sfateo\'o! 9 
In applying the condensed gases‘as 
mechanical agents,’ there will be’ some 
difficulty ; the materials of the apparatus 
must be at Icast as. strong,and.as per- 
fectly joincd as those used Jy, Mr. 
Perkins in bis high pressure. steam- 
engine: but the small differences, of 
temperature’ required’ to produce an 
. a er ada He 
asf P cao? 
SEG! SESS Ue ee eee 
* Since this paper was read, Mr. 
Faraday has ascertained that the vapour 
of ammonia at 32% exerts an elastic forte 
equal to that of anatmosphere comptessed 
to t; and at 50° o that of an atmosphere 
compressed to 49: and that the vapour 
of nitrous oxide at 32° hasan elastie force 
equal to that of an atmosphere compressed 
to 7;; and at.45° to an atmosphere com- 
4) 
1, 
pressed to = nearly. 
51,3 
