1908. | Groups of Waves in Dispersive Media, etc. 420 
Table I. 
¢ = relative amplitude, along the same crest at different azimuths. 
a 
w 
SS OC oa 
IS 
© © 
8 Kard 
° 7 2 aT one 
{¢) 4 8 12 16 19e820 
Fia. 5. 
(b) The diverging wave system.—By taking the smaller root for cu given by 
(77), we obtain the system of diverging waves; we need only change the 
sign of the radicle in order to write down the corresponding results in this 
case. 
The crests of the waves are given by 
ga/2 {8.cos «—(9 cos? «—8)*}? 
16c? {3 cos? a—2—cos a (9 cos? a—8)}* 
= (2n+4)r, (87) 
When « is zero, w is also zero; thus all the crests diverge from the point of 
impulse. Further, we have 
3S C097! D/AYS 2 w= 20? (2n+8)/g/3. (88) 
23 
