DKVKLOPMENT OF THK PrNK KANdK. 13 



main luxly of tin- oxtrcmity of tlir (":iiu'; ((!) the pivseiicf of sITm-ilc 

 or foarse l)c'a(li doposit.s uiuleilyiny the dunes in phices, and on the 

 «anie K'vel with the present beach. 



If this be the method of dei)osition it follows that the nceessity for 

 sand lixatit)M will never cease unless the sand supply for the shore 

 drift becomes exhausted. However, the process of sand accunuda- 

 tlon is so comparatividy slow as to be of little imi)ortance when com- 

 ])ared with the njore serious conditions incident to the extensive areas 

 of only partially reclaimed sand dunes. 



Development of the Dune Kanoe, 



It is probable that each of the seven dune rant,'es which constitute 

 the «,neater portion of the extremity of the Cape was developed in a 

 similar manner, from the successive beach rid«,a's and ensuin*,' fore- 

 dunes, l)v the accumulation of the sands l)lown up from the beaches. 

 The vej^etution has been an important factor in their lormation, and 

 althouLdi the intermediate stuws between the foredune and the forested 

 dune range are f ra»(mentary the general se<iuence of events is evident. 

 As soon as the sand deposited by the waves is blown up to beyond 

 the action of the tides the beach grass, associated with the typical 

 strand vegetation, spreads rapidly over the surface and retards the 

 movement of the resulting l>each ridge. As the sand accunudations 

 continue, the ridge becomes a foredune. Tlu^ l)each grass pushes its 

 way up through the accumulating sand by the formation of new root- 

 stocks, thus keeping the ever-increasing area of sand comparatively 

 well covered, as the gradual addition of sand constitutes one of the 

 essential conditions for the ideal growth of the grass (PI. II, fig. 1). 

 The foredune continues to rise and other species of plants come in, 

 but ultimately a height is reached where the unbroken winds are of 

 sufficient force to prevent the vegetation from holding the sand. At 

 this stage the long foredune becomes a dune range and begins to move 

 inland, covering tlie preexistent vegetation in its path (Fl. IV, Hg. 1). 

 The movement continues until the dune range is sufficiently removed 

 from the unl)roken force of the ocean winds to permit the develop- 

 ment of a vegetative covering dense enough to prevent its movement. 

 The forested condition ultimately dominates. 



The development of the succeeding beach ridge and foredune may 

 have been rapid enough to afford some protection to the preceding 

 dune range, and thus hasten its fixation by the vegetation which would 

 develop more rapidly under the protection afforded by the new^ fore- 

 dune. 



This beach ridge is of two possible origins. It may be formed from 

 the normal sand accumulations cast up by the waves along the old 

 beach, after the dune range migrates inland, or it may develop from 

 the sand spit or bar which is added to the mainland as first indicated. 



