x 
J. H, Alexander on the Tension of Vapor of Water. 221 
Mr. Dalton’s experiments. were distinct; and are therefore 
given in distinct columns. The numbers in the earlier column, 
marked with an asterisk, were not from actual experiment ; ee 
> interpolation, according to the method he has himself 
. [have inserted them opposite. to amen mig numbers i 
pd adjoining column, for the sake of comparison and the igiee 
fit of the inference which may. flow en the variations. The 
numbers in the later column were not, in every case, bagi by his 
own experiments ; but they were accepted by him as authentic, 
and the most reliable he knew. It is more complimentary to 
his reputation than to their own research, that compilers of Chem- 
ical manuals, even down to the present time, retain among their 
tables his ancient results whose inaccuracy he himself -has_ re- 
cognized. All of his experiments, of Southern’s, and of Dr. Ure’s, 
are in the table. ‘To the originals of Mr. Arzberger, .I have not 
had access; but I have found these quoted, in. so many authorities 
and so uniformly accordant that I have not hesitated in recording 
them. Of the extensive table of Mr. Taylor,.whose remarkable 
call attention to, I have taken only those epochs of sateen 
ture which were already in my table. - 
The experiments of the French, Academy have been already 
signalized. It is enovigh to establish their claim to distinetion, to 
say that they were executed by Dulong and Arago ; 
have been long since inscribed in the very highest. rank of phys- 
ical philosophers. The numbers found im the appropriate col- 
umn, are, agreeably to what [ have already vaacrron o. as ete 
ing me throughout, quantifies actually-observed. ‘The tempera- 
tures.and pressures. generally quoted in the text-books on Steam, 
as of the French Academy, are not, in fact, what they observed ; 
but what they deduced (in part, by a formula of their own, and 
in part, by 'Fredgold’s) from the present experimental . series. 
The pressure 29-92 inches Smee to the temperature 212°, 
is marked with an asterisk, because it is not expressly declared 
to have been observed: It is the height which is cons 
taken in France for the barometric standard, as thirty inc 
in England: in the latter assumption, the temperature is rated at 
60° F.,—in the former, at 32° F.; and the difference of heights _ 
is seta identical with the difference of expansion at had Te 
Pective temperatutes. 
ressure inthis series corresponding to the tem 
368°: “B14 is also noted with a’ dagger; it may be ree m2 
erroneous, not only because it differs so much from the result by 
my formula, but because it varies so much and so suddenly from 
the rate accused by the pressure on eitherside of it. Nor does it 
co at all with their own formula ; calculated by that, the 
pressure will be 335-87 inches. The error is net, po hl 
Seconp Serizs, Vol. VI, No. 17. —Sept., 1848. 
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