Propagation of Groups of Waves in Disperswe Media, etc. 480 
With the help of these results, sketches are given in fig. 9 to represent 
the change in the wave pattern, as the critical velocity is approached and 
passed. 
tEditorial Note [The shapes of these wave-fronts have been recalculated by 
Inui (Physico Mathematical Society of Japan, Vol. 18, pt. 2 {1936]) who 
does not agree that they are concave to the axis. | 
HaRRISON AND Sons, Printers in Ordinary to His Majesty, St. Martin’s Lane. 
33 
