304 



ALEXANDER AGASSIZ 



The mushroom rock is eaten away, or rather pounded 



away, along the 



■O 



h.wm. 



L.W. M. 



Fig. 6 



Fig. 7 



line J. C [Fig. 

 6], leaving a 

 crescent - shaped 

 wall at the level 

 A, and the water 

 all falls out at C 



[%• 7]- 

 At the foot of a vertical cliff a ledge is frequently 



formed [Fig. 8], and the surf 



during low tide pounds over 



A and cuts away all the dotted 



part A C, forming a regular 



harrier reef at the foot of the 



cliff, with as much as eight 



feet in one case, a regular 



slope from A to C. If this 



slope is protected by Algae or corallines, it is not eaten 



away, otherwise 

 it may make a 

 pothole inside 

 the wall. Then 

 vertical walls are 

 of all shapes, 

 winding around 

 and twisting, 

 forming all kinds 

 of reentering 

 curves [Fig. 10]. 

 Now before I 

 had seen these 



Serpnla3 atolls, I had come to the conclusion that the 



TH.W.M. 



