94- Mr. Ivory on the Theory of the Astronomical Refractions. 



a (14-«) ^\ (. , d» I di\ f. 



de d^ 



e ' de 



d\ 



•^Qi} 



Now de _ 1 di l—e^ 



~e~ ~ '2 ' T ' 1+e^ ' 



dK ^ da. di 

 K ~' a. i ' 



wherefore, 



^ a, I 



. , «(!+«) di(S 1 1-e^ <ZS \ 

 — sin 9 . ^ .: . -r- f — . r . -7— e ) 



. a (1+a) fda di^ ^ „ 



If ;j denote the observed height of the barometer, reduced 

 to the fixed temperature of 50° Fahr. ; and t the temperature 



of the air on the same scale; then B = — , 



^ 480 



1 . If^ - ^ P_ 



^^ a 1+i8(t-50)' so' 



da. _ _ T— 50 30— j9 

 "cT ~" 480 30 ' 



d i _ T— 50 



7~ ~ "^ 480 ' 



— — — = — 2 X T— 50 30—;? . 

 a e "" 480 30 



These values being found, if we put 



T = sin9x \— . xttt; xf ' ^^ , g, q ) 



. , «(l+a) 2XQ, 



the expression of the mean refraction with its correction will 

 be as follows, 



