28 N. M. FENNEMAN 
unless the power of inward transportation is decreased before 
reaching the shore, no barrier can form. This decrease may, 
at times occur, for carrying power will depend not only on the 
velocity, but on the agitation of waves at the bottom. It has 
been seen that waves are rapidly reduced in size and vigor in 
the act of breaking. It is possible, therefore, that when the 
slope is so gentle that waves recover their form after breaking, 
thereby showing that oscillatory wave motion has been much 
reduced, deposition may take place along the line of wave reduc- 
tion, which is essentially the breaker line. With these condi- 
tions alone, however, the growth of this feature would probably 
be confined to narrow limits by the undertow. It would, more- 
over, be a very transient feature, a mere incident in the process 
of shoreward transportation. The steepening of the shore, to 
which this process is incidental, would rapidly remove the con- 
ditions of the incident. 
Variations of the compound curve.—The compound curve will 
be more marked in proportion as the surface of deposition is 
broad and its slope is gentle. Where it is narrow its significance 
may not appear from a profile drawn from widely spaced 
soundings. If all the waste from the land be carried along- 
shore, the marginal terrace is of the cut type purely, in which 
the compound curve is not noticeable, the only prominent angle 
being that where the surface of cutting intersects the original 
steeper bottom. 
Currents alongshore.—If the effect of currents alongshore 
were the same at all distances from land, they might be ignored 
as a factor in profile making. Their variation in strength at 
different distances from shore produces important results. It 
has been stated above that for any one current the power at 
the bottom with respect to the load must remain constant. It 
may also be shown that of éwo currents, each of which is furnished 
with load to its full capacity, the stronger, which may be sup- 
posed to dissipate gradually, will be in equilibrium with its load 
at the smaller depth. Hence if transportation alongshore be 
t This is illustrated at many places on the Pacific coast of the United States. 
