504 Mr. Lubbock on the Pleat of Vapours 



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

 stituted in the equation 



x = u co*, (p. 489) 



p 



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. so that 



' ag 



X = log ( 1 co) +/log (1 co) H 



= log (1 co) +/log(l co) + hw. 

 This equation corresponds to the equation of Mr. Ivory 



x = u - A (1 - c-u) -f ( ^^ (1 - 2 f ^-^njr - &c. 



p. 203, when /' =0. 7? 2 = 1 u c-u co = 1 c-*. 



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

 upon the supposition thatjf', y", &c. = 0. 



Let i' x 1 = _^( ] +0(1 -_/) log (i _ ,) 

 as v 



and let f = 



.) (I-/) 



x 1 = log (1 co) -f h 1 co 



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

 ters by Mr. Ivory, if 



a = -0002835, i - '0012958, h = -22566, /= - 



then i 1 = -0010078, h'= -29012. 



By Lagrange's theorem I find 



* Mr.Ivory has the equivalent equation = \-*ti = ix-^-eiu t p. 203. Mr. 



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



