412 Professor Airy on the Phenomena 



._ cost / _ tan (t - t') N 

 ^"cosTV ~ tan (« + «')/ ' 



_ tan (»' — «") 

 ^~ tan («' + <")' 



,_ tan (i - t) 



tan («' + <) ' 



, _ cos/ / tan(i' — <)\ 

 cosi V tan(/+i)/ ' 



Hence fk = 1 -e i , and gk=—ge; and the expression becomes 



sin(^-*)-r) + ^. s in(^(*7-,Q) 



Resolving' this into the form 



sin—- (vt — x) + Qcos — (w^-a;), 



the intensity or P 2 + Q 2 becomes 



^ g- + e 2 + 2ge cos P" 

 1 + 2ge cos V+g^e*' 



The maxima and minima of this correspond to the maxima 

 and minima, or the contrary, of cos V. When V=Q, 2tt, &c. that 



X 2\ 



is when P=0, or = 7 , or = - -, , &c. the intensity of the 



2 cos < 2 cos i J 



reflected light is 



VI +gej 



