390 



Mr airy, on the INTENSITY OF LIGHT 



X 

 as above, is shewn to be 



3«'X\* 



Making -7- •^-5*'= 5'"''' ^^ ^ = (^r~) • "'' ^"*^ putting m for 

 " X I —5- 1 , and omitting the constant factor, the intensity of light. 



[X, COS - (jc' - m . w)y, 



the integral being taken from w = to w = infinity. 



It will be remarked that m, in this case, is proportional to -~ — ; 



it is therefore for points in the direction of the asymptote, and for 

 other points it is proportional to the angle made by the line from the 

 center of the wave with the asymptote. 



17. The values of f^ cos „(«''— »«• w), from w = to w = infinity, 



and the squares of these numbers, for every 02 from m = — 4-0 to 

 m = + 40, are contained in the following table: for the calculation of 

 which I refer to the Appendix. 



