1890.] NEW YORK ACADEMY OF SCIENCES. 21 



to seaward, and this process to continue until three or four cays 

 were formed one outside of the other, it seems as if the first one 

 would be higher above the level of the sea than the last, and this 

 Agassiz ' states is not the case. When I first read Agassiz's 

 memoir I was much impressed with the strength of his argu- 

 ments. But Heilprin's in regard to elevation are conclusive; 

 and although he did not visit the lower part of the Peninsula, 

 it is probable that its movement is in the same direction as that 

 portion examined. 



It will, however, be noticed that Agassiz lays no stress on the 

 effects of the erosion that takes place so rapidly on all islands of 

 coral formation. 



I believe that the views of these two eminent observers can be 

 brought into harmony by considering the effects of erosion. Let 

 us suppose a cay has been formed of calcareous material thrown 

 up by the waves to a height of fifteen or twenty feet. Then, 

 while the cay to seaward was being formed, the erosion would 

 take place on the one already made, and whether its height 

 above the sea increased, remained constant, or decreased would 

 depend upon the relative effects of the elevation and erosion. 

 It is not improbable that these two forces might balance each 

 other; and if this were so, it is easy to show diagrammatically 

 that any number of cays could form, one after the other, to sea- 

 ward, and yet the first be no higher than the last above the 

 level of the sea. And this argument also applies to the cays 

 near Nassau. It is probable that the ocean would throw up 

 some of the cays higher than the others, and also that a slight 

 difference in height would not be observed by the unaided eye. 



27ie Formation of the Balimiias. 



Asstatedon page 4, the islands lie on the eastern and northern 

 edges of the Great and Little Bahama Banks. The only excep- 

 tions are Great Bahama Island, the Biminis, and some others 

 that are exceedingly small. 



As I have visited only New Providence and Andros, I hesitate 

 to do more than suggest that the other islands of the banks have 

 been formed by the action of the waves and wind in the same 

 manner as the cays near Nassau. 



A visit to the other islands of the srroup would be well repaid, 

 for some of them, as San Salvador, Rum Cay, and Inagua, have 

 apparently been formed in a different manner from those on the 

 Great Bank. And it is interesting to note that Dr. Bryant '' de- 



1 "Report on Florida Reefs," Mem. Mus. Comp. Zool., Vol. VII., No. 

 1, p. 36. 

 2Proc. Best. See. Nat. Hist., XL, p. 63. 



