THE RAINBOW DUE TO A CIRCULAR SOURCE OF LIGHT. 21 



then plot a curve whose ordinate is equal to the product of the 

 vahie of /^ into the corresponding ordinate of this circle ; the 

 area of the new curve divided by the area of this circle is the 

 value of F at -/M. The followinir table has been made according 

 to this method. 



litif=a])pai'ent diameter of the sun = 32' 

 yj : (except 0) max. and mini, of Airy's value. 

 In Table I 



F, : r=0.02r) cm. /=5893xlO-^ cm. x = 120.95 

 Fo : r=0.05 cm. ;. = 5893 x 10"' cm. x = 192.00 



TABLE I. 



The graphical representation of this table is given at the 

 end of the paper, where /" is represented by the dotted, Fi by 

 liruken and F 2 by solid lines (PI. I). 



