414 



A. Agassis — Notes from the Bermudas. 



or convoluted or looped vertical walls of broader ledges which 

 stand up from the bottom and seem to have been built up by 

 the organisms covering their surface. Taking this for granted 

 as had been done by previous observers, I was greatly surprised 

 on hammering at some of these structures, to find the vertical 

 walls composed of asolian rocks and to discover that in many 

 cases the elevated rim was protected by the hard ringing crust 

 so characteristic of limestones exposed to the action of the sea, 

 and further to find that the coating of Serpulae, of Algae, of 

 Corallines and Xullipores was quite superficial. It soon became 

 evident that these diminutive atolls were large pot holes exca- 

 vated by the surf and sand and that the varied forms of cres- 

 cent-shaped reef of barrier reefs and all the possible modifica- 

 tions one finds on the south shore of the Bermuda are all due 

 to the mechanical action of the surf. 



The following diagrams will explain their mode of formation 

 better than any lengthy description I can give. 



AB (fig. 1) is a piece of shore cliff which has become isolated, 

 the aeolian lamination is clearly seen above high water mark. 



Below high water mark it is 

 honeycombed and eaten away, 

 leaving the aeolian pinnacle 

 supported only by a slender 

 stem rising from an extensive 

 base more or less covered with 

 Algae, Serpulae and other 

 growth. The surface of the 

 ledge as well as the base of the 

 mass extending below low 

 water mark is more or less 

 eaten away and when the aeol- 

 ian pinnacle (A) has fallen off 

 a mushroom-shaped mass is 

 left, the upper surface of which may be above or below low 

 water mark. All trace of aeolian stratification has been oblit- 



^ Vm erated by the cementing and 



solving action of the sea water. 

 If the base, the mushroom-shaped 

 ledge, is stratified horizontally 

 (fig. 2) the result of the wash of 

 the breakers upon any part of 

 the top left unprotected will be 

 to dig out circular or elliptical 

 atolls (fig. 3) like A or B. In 

 one case A the atoll will have a 

 rim of nearly the same width, 

 while in the other case B, if the 



FiCx 1. 



Figs. 2-3. 



