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 althongh 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 toa 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. 
The Formation of the Bahamas. 
As stated on 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 group would be well repaid, 
for some of them, as San Salvador, Rum Cay, and Inagua, have 
apparently been formed in « 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. Zo6l., Vol. VII., No. 
Tp. 36. 
? Proc. Bost. Soc. Nat. Hist., XI., p. 63. 
