1822.] C.’s Reply to D. 197 
acknowledges it to be nearly, and I confess many circumstances 
lead me to conclude it to be strictly the case. In the absence of 
proof, I do not wish to dogmatise. I shall, however, briefly 
advert to a circumstance which appears to me to render any but 
the simple relation inadmissible. It is well known that at a 
given temperature, the densities of gases are as the forces which 
compress them. From this fact, and Newton’s expression for 
the elasticity (see any work on pneumatics), it follows that their 
particles repel each other with a force which varies inversely as 
the distance between their centres. Now if the density of steam 
be not as the force which compresses it, or in other words, as its 
tension, it must follow that its particles repel each other accord- 
ing to a different law, a circumstance improbable, when we con- 
sider the accordance of its expansion, when apart from water, 
with that of gases. This argument, however, I am not disposed 
to insist upon, as my principal object has been to show, that 
Mr. Herapath’s formula does not comprehend vapours in contact 
with their fluids. 
Your obliged humble servant, 
James APJOHN. 
Articte VII. 
Observations upon D.’s Answer to C.’s Remarks upon Mr. Hera- 
path’s Theory. 
(To the Editor of the Annals of Philosophy.) 
SIR, 
I aM sorry again to occupy any space in your Annals on the 
subject of Mr. Herapath’s theory, but the observations of your 
correspondent D. require some notice from me, and will excuse, 
I hope, my wishing once more to trespass upon your kindness. 
Had he indeed confined himself to reasoning, I could without 
concern have left it to your readers to have determined whether 
or not my objections to that theory were satisfactorily answered ; 
but by the charges he has made against me, lam obliged for my 
own Satisfaction again to obtrude myself upon you. His manner 
indeed [ do not complain of, as he seems to think it natural I 
should; he has no doubt chosen that which he thinks the most 
effective and convincing ; and I may, therefore, with as much 
reason, complain of his differing from me on any other subject as 
on the propriety of that manner. 
One of the charges to which J allude is more applicable to a 
moral than an intellectual deficiency ; and consequently, if true, 
would be a disgrace, instead of a misfortune. It is contained 
