216 



PROCEEDINGS OP THE AMERICAN ACADEMY. 



by transportation and accumulation in front of the nipped oldland. 

 Although plotted from the soundings and contours about point Wilson, 

 this figure will serve as a general profile of all the cusps of this class. 

 Where the initial slopes were less steep, less contrast is seen between the 

 oldland and the foreland. 





.SL 



Kilometers. 



Figure 24. Profile of Tidal Cuspate Foreland : Point Wilson, Washington. 



Tidal Hypothesis. — Before considering other cusps which differ some- 

 what from West point, let us look for a moment at what might be 

 expected to result in narrow channels with sides nearly parallel. Waves 

 would attack this inner shoreline to a greater or less extent at all points. 

 When adolescence is reached in the process of shore development, and 

 waste is supplied faster than it can all be carried offshore, it will be 

 transported and deposited somewhere* The great system of ocean eddy 

 currents is not able to affect this inner as it does the outer shoreline. 



Local winds must pro- 

 duce small currents pro- 

 portional to the size of 

 the water bodies, but 

 these will be so weak 

 in narrow channels that 

 their effects will be lost 

 in those of even mod- 

 erately strong tidal cur- 

 rents. Thus it seems 

 safe to conclude that the 

 probable agent of trans- 

 portation in such chan- 

 nels is the tidal ebb and 

 flow. 

 An ideal scheme of inflowing tide, with the eddies which would prob- 

 ably accompany it, is given in Figure 25. Where the movement is 

 least in the triangles of comparatively dead water between the several 



Figure 25. — Ideal Scheme of Tidal Inflow : Port 

 Discovery, Washington. 



* Compare pages 176-178. 



