<7 
U 
iS 
@ 
Ta) 
PROPAGATION BY PIPINGS OR CUTTI 
WN 
Lg\ aN 
== 8 ey, 
= — 
-—— —— —— ———— —— 
SS ——— 
—_ = 
FIG. 22,—Sce opposite page, also Chapter IV, 
