20 TRANSACTIONS OF THE [ocr. 13, 
reef at Nicols Town, Andros, and also that at Rose Island, near 
Nassau. 
At Nicols Town the reef was about a quarter of a mile from 
the shore, and the water varied from ten to eighteen feet in 
depth. The reef was almost entirely composed of the great 
Madrepora palmarum, with some small patches of M. cervicornus. 
Both of these corals were growing luxuriantly, and their tips 
were close to the surface of the receding waves. ‘The reef at 
Rose Island, however, contained very few specimens of M. pal- 
marum, but many of M. cervicornus, and also large heads of 
what are popularly known as ‘‘ brain corals,” but which of the 
genera so designated I am unable to state. The receding waves 
left the top of the reef bare, and exposed the sea fans and alcyo- 
noid corals that were growing on the top. ‘Toward the shore the 
reef sloped gradually downward into a bank of sand, or, in other 
words, the sandy bottom sloped upward to the top of the reef, 
which thus presented a very different appearance from the one 
at Nicols Town, where the corals rose from the bottom. These 
facts show, I think, that the Rose Island reef is an old one, while 
the Nicols ‘own reef is in what we may call its prime. Astudy 
of the chart of New Providence shows, running along its north- 
ern shore, a number of reefs, some of which are marked. nearly 
dry at low water. Now, in order to convert these reefs into land 
it is only necessary that they should be slightly elevated or that 
sand should be deposited on top of them. And this, I believe, 
is the way in which the cays known as Hog Island, Rose Island, 
Salt Cay, and Quarantine Cay have been formed. In other words, 
I believe they have been formed in the same manner as J. Agas- 
siz explained the formation of the cays of southeastern Florida. 
He argues, however, that as the cays nearest the land, and hence 
those first formed, are no higher than those farther seaward, it 
follows that during their formation the land was stationary. 
Prof. Heilprin,’ on the other hand, has proved that the Florida 
Peninsula is, or has lately been, rising. I think I have shown 
that the Bahamas, or at least the islands of New Providence and 
Andros, have very recently been rising; and yet, although I have 
no measurements, I venture to state that Salt Cay, the most sea- 
ward one, is as high if not higher than Hog Island, that lies in- 
side of it. 
To return to Florida. It would seem at first as if the conclu- 
sions of Prof. Heilprin precluded the possibility of the cays be- 
ing formed as suggested by Agassiz; for if we suppose a cay to 
be formed while the land is rising, and then that another forms 
1 Trans. Wagner Free Inst. Sci., Vol. I. 
