WITH AN APPENDIX BY PROFESSOR A. LODGE. 



99 



The next three terms, written without regard to sign, and their di (Terences are as 

 follows : 



The remainder is found, as before, to be 



+ (-3688) + i('0218) + -J (-0040) = + "1903. 



The sum of the infinite series from the beginning is accordingly 



+ -1871 - '2467 i (28), 



(1871) 8 + ('2467) 2 = -09588. 



in which 



The distance between the source and the point of observation is now 

 2csin45 = c. v /2. 



The intensity in the actual case is thus '09588 as compared with '5 if the sphere 

 were away. 



For other angular positions than those already discussed, not only would the 

 arithmetical work be heavier on account of the factors P,,, but the remainder would 

 demand a more elaborated treatment. 



O 2 



