as deduced hy himself and Dr. Suerman. 265 



If therefore we revert to the equation 



and substitute in it for m' and m their values, namely <f, and 



e f 



— X - — X '625, we are conducted to the following final 

 as 30 ^ 



equation, which includes the solution of the dew-point pro- 

 blem, 



sad V _/',_48s«^ ^_ 



In the case of atmospheric air 5 = 1 ; so that for the pur- 

 poses of the meteorologist 



/"=/'- i^x^, (B.) 



e 



which, if we assume a — '267, and e = 967° + 212° —50° 

 = 1129, becomes 



/-// _ /-f _ A X A 

 •^ -^ 88 30 ' 



the expression which I have used in my paper on the dew- 

 point. Now though a and e are not, as is assumed in this 

 latter expression, constant, the mean values which are assigned 

 to them are sufficiently exact for all practical purposes. This 

 I believe I may say I have established by three distinct series 

 of experiments, for the particulars of which, however, I must 

 refer to my second paper on the dew-point. 



Before proceeding to other topics, I wish to state that an 

 expression identical with (B) was obtained some years ago by 

 Mr. Ivory. His method, however, was so totally different from 

 mine, that those who examine both will, I make little doubt, 

 consider it scarcely necessary for me to disclaim, as I have 

 elsewhere done, any knowledge of his investigations at the 

 time I gave publicity to my own results. In perusing also 

 Dr. Suerman's thesis already referred to, I find ascribed 

 to Gay-Lussac a formula for dry air which scarcely differs, as 

 shall be hereafter shown, from one which may be deduced 

 from mine. Again, in the first part of Professor Graham's 

 Elements of Chemistry recently published, and which he was 

 good enough to send me, I find, in a note to page 82, a 

 formula ascribed to Dr. August which is in form the same 

 with that which I have given, but adapted to Reaumur's 

 thermometer. The coefficient, however, of d is too great by 

 about one fourth ; for the formula in question (adopting in it 

 the notation already employed,) is 



