% 
J. H. Alexander on the Tension of Vapor of Water. 215 
temperature above the maximum) is 0:99944 of the same unita- 
ry volume :—an accord which, considering the possible errors 
of the experiments, appears to me sufficiently satisfactory. 
The equations already given serve to find the pressures in inches 
of mercury and in atmospheres respectively, when the tempera- 
tures are given: to find the temperatures corresponding to given 
pressure, they ae as follows ; 
180 /p— 105°-13 ; 
where p represents the ye of ata of wre ot and 
13 Vp'— 
where p’ stands for fe Sita of adobthictte 
After these preliminaries, may now 5 Lapeer the compar- 
ison of results by the formula and by the experiments of vari- 
ous observers; as is done in the following table. 'This table is 
quite extensive ; and, for my own sake, rather more so than I de- 
ired. But it will be considered that it comprehends the assem- 
blage of the sibastitions of many persons through many years ; 
and it was, besides, to me of an interest that I think will be par- 
taken of by others, to have in one view and without interpola- 
tion saat all the Pee ee a that have been made by actual 
ment. In lim it to statements of this character, I con-’ 
fess L thought at fie é restrict its extent, though it appears that 
there are in fact more experimental data than is generally sup- 
posed ; and I desired besides to increase its utility beyond the 
mere comparison with the present formula, by fitting it as a de- 
pository for general reference. i this last regard, it may be 
considered as authentic and reliab 
And yet after all, it does not ite the whole of our experi- 
mental data. Those of John Henry Ziegler, of Winterthur in 
or only in statements at second or third hand, whose accuracy I 
had not the means of verifying. 
Nor does it contain quite all the results of those observers to 
whose experiments I had access. 'T'o have given every one of 
each, would have ash the table, in respect to the eect 
of Mr. 
cised, therefore, the discretion of using only those instances 
which, at reasonable degrees apart, rested upon a number of con- 
