CHARACTERISTICS 611 



the slow obliteration of others ; or if the new waves are very large, there 

 may be a rapid obliteration of the earlier series of ciisps, followed by the 

 slow formation of a new series adjusted to the size of the later waves. If 

 the widely spaced cusps formed by large waves are attacked by smaller 

 waves, so much of the older cusps as can be reached will be eroded and 

 the material refashioned into smaller cusps more closely spaced, regard- 

 less of the positions of the older ones (figure 4) . When large and widely 

 spaced cusps are built by high storm waves well up the slope of the beach, 

 only their apices are apt to be attacked by the smaller waves of calmer 

 weather, and so it happens that we commonly find the largest cusps par- 

 tially preserved near the top of the beach, with series of smaller and more 

 closely spaced cusps farther down the slope. 



Eegarding the building of beach cusps, Jefferson writes (1899, 246) : 

 "If it be asked how this begins, the answer must be that the beginning 

 is as old as the beach. . . . Each set of cusps may modify its suc- 

 cessors. A new crest of seaweed flung up today is likely to have its weak 

 points in some measure determined by the previous channels. In violent 

 storms it is doubtful if this control is significant. Each storm probably 

 sets the shape in which the waves must play for a long time." If we 

 accept Jefferson's theory of cusp formation, the conclusions just quoted 

 would seem to be reasonable. But the sensitiveness of beach cusps to 

 changes in size of waves leads to quite opposite conclusions. Instead of 

 the beginning of cusp formation dating back indefinitely, there appears 

 to be a new and quite independent beginning with every marked change 

 in the size of waves. One set of cusps seems to have little influence on 

 the position of its successors. Along the shores of a little bay just south 

 of Huletts Landing, Lake George, cusps built by small waves are com- 

 pletely obliterated each day by three or four of the large waves which 

 strike the beach after the passing of a steamboat. Opposite the cusps, 

 but farther up the beach, pegs were driven to mark the position of the 

 cusps. After their obliteration they formed again under the influence 

 of the small waves, with the same size and bpacing as before, but, as 

 shown by the pegs, in totally new positions. The law controlling the 

 relation of spacing to wave size was operative, but the cusps which were 

 there a few moments before did not determine the position of their suc- 

 cessors. The same phenomenon may be observed in the production of 

 artificial cusps. Furthermore, if a series of parallel trenches be exca- 

 vated in the artificial beach at right angles to the shoreline, the inter- 

 cusp spaces and the cusps will not correspond with the trenches and in- 

 tervening ridges which have been made to guide wave action. In fact, 

 waves of a given size insist on forming cusps at appropriate intervals. 



