62 SIR G. GEEENHILL ON ELECTROMAGNETIC INTEGRALS. 



To reduce Q l to this standard form, put 



(3) 2av/(A 2 + //)+2Aacos0 = ro 8 ( Tl -0, 



6 a -2Aa = ro s 



... . fV- 



(4) iA - 



J h T! 



and to reduce Q 2 , put 

 (5) 



8 ) = [a + 



Then the sequence runs 



(7) 00 > t, > T, >t, > t > t, > T 2 > - 00, 



and we take 



(8) 



(9) / 2 G' = 



v/ - 



(10) Q, = x/ +.2G zn/G', Q s = 7T/ + 2G zs/ 2 G', 

 and with / 2 -/, = 2/ 



(11) Q (PZ) - 27T/+2G zn 2/G' + 2G y ' sn 2/G' 



- Q(MQ) = 27T-Q. 

 Interpreted geometrically on fig. 2, with 



(12) sn/G' = 



i-A 



+ A' 



