268 
Frank Carney 
and off-shore slope. Ultimately these agencies under normal 
exposure to waves will bring about a fairly uniform and constant 
profile which is a gentle long slope into deeper water. The time 
required for a given body of water in a particular locality to pro- 
duce shore line structures, depends very largely upon the original 
outline of the coast: if sufficiently irregular, and if it yields quickly 
to these denuding agencies, a supply of material will be at hand 
for constant work. 
It is in the production of this material that the chemical process 
figures. In the presence of water, chemical disintegration is 
facilitated. This is important even when the coast being attacked 
consists of unconsolidated deposits. The basic elements of glacial 
drift break down more readily, leaving the acidic for distribution 
by waves. 
But the more effective work in the preparation of material is 
accomplished locally by the waves of translation which erode the 
shores producing bluffs, that in turn are under-cut by wave-impact 
and the tools the water has in it. This on-shore movement of 
water likewise grinds the constituents of the beach, rounding and 
diminishing the size of all the stones. The along-shore move- 
ments also do much attrition work. Furthermore, as the waves 
of greater size break off-shore, they pick up bits of rock, dashing 
them again to the bottom, thus continuing the work of attrition 
begun nearer shore. 
All this material is being distributed likewise by the water. 
Beach ridges represent the ascendency of the work of water mov- 
ing on-shore over that accomplished by the water moving outward, 
that is, the undertow. Whenever the dash of oncoming waves 
drives material up the slope beyond the effective reach of the under- 
tow, that material becomes part of the beach ridge. The ridges 
represent the work of unusually strong and more directly on-shore 
movements; an equally powerful on-shore wave, striking the coast 
obliquely, is not so effective in constructing ridges. Since the 
beach ridge, then, represents a differential of these quite opposing 
movements of water, it follows that the shape of this ridge is also 
the result of this difference. The undertow cannot carry any save 
the smaller bits of rock, and only the finer portions are carried 
very far off-shore. Material in suspension is always the finest 
product of destructive work and will be taken farthest from the 
shore line. The front slope of a beach ridge has a long gentle 
