504 Mr. Lubbock on the Heat of Vapours 



When u is a simple function of co, this value of u may be sub- 

 stituted in the equation 



a; = u rev*, (p. 489) 



and the value of co in terms of x may be found at once by the re- 

 version of the series. 



Mr. Ivory makes — = i 9 so that 



X = - log (1 - co) +/log(l - co) + J^f-^ CO 



= — log (1 — co) +/log(l — co) + ^<0. 

 This equation corresponds to the equation ot Mr. Ivory 



p. 203, when /' = 0. J? 2 = 1 - w — c-« co = 1 — c-w. 



The table of mean refractions given by Mr. Ivory is founded 

 upon the supposition that/ 7 , f ] \ &c. = 0. 



Let z' #' = a 1 L± jU loor (1 — co) 



andlet^ ^ 1+ -^l^/) =a _ /) , 



# ; = — log (1 — co) + h' oj 



i and h are identical with the quantities represented by those let- 

 ters by Mr. Ivory, if 



a = -0002835, i = '0012958, h = '22566, f-\ 



then z 7 = -0010078, h'= -29012. 



By Lagrange's theorem I find 



* Mr.Ivory has the equivalent equation — = \-a,u = ix-\-uu, p. 203. Mr. 



Ivory's a is a i u in the notation of this treatise. 



