18 N. M. FENNEMAN 
true breakers (not whitecaps merely) may occur during a wind 
on a shore where waves of the same size would not break ina 
calm. 
Effect of breaking on wave propagationn— Even when the 
distortion of wave form has been pressed beyond the breaking 
point, the effort to recover its form and habit does not cease. 
This effort is now favored by all the tendencies which existed 
before breaking and re-enforced by one more arising from the 
falling crests. As shown in the diagram (Fig. 4), breaking is 
an expression of conflicting orbits. The water above the node 
of the hypothetical surface does not continue the curve which it 
has been describing, but falls confusedly on the front of the 
wave. Here its downward motion is in direct opposition to the 
upward motion of the water in front of the crest. Thus, to the 
molecular resistance of friction, is added mass conflict, both of 
which operate to reduce wave motion. This reduction is there- 
fore accomplished more rapidly than in the case of unbroken 
waves. It results from this, that waves often break at some dis- 
tance from shore, and after traveling a short distance with foam- 
ing crests, recover their form and advance a long distance with 
crests entire. There is a certain slope on which waves will 
advance with nearly uniform shape and continuously foaming 
crests. On a gentler slope they will recover their unbroken 
form; ona steeper slope the first breaking occurs close to shore, 
and the wave form is speedily lost. 
Waves of translation.—W hen waves of oscillation enter shallow 
water the habit of the water particles changes and becomes a 
compromise between orbital oscillation and movement of an 
entirely different nature, belonging to waves of translation.* 
The essential features of the positive wave of translation, 
known also as the wave of the first order or the solitary wave are, 
(1) it is initiated by an elevation of the water surface above its 
normal level; (2) it is propagated without a corresponding 
trough and without companion crests, being entirely above the 
undisturbed level of repose; (3) its rate of travel is greater 
TRUSSELL, Report on Waves and Wave of Translation. 
