E. B. Hunt on the Florida Reef. 209 
have been more than once used by the coral animals, and some 
must have been swept into the ocean waters. ‘Taking the living 
reef at one-twentieth the breadth of the total bank, the depth 
of the bank at three hundred fathoms, and the rate of growth at 
2 inch per annum, we find, aside from the other elements of 
being by the west end from Cape Florida to Tortugas Bank, a 
great increase of time is still demanded, so that we can hardly, 
on these data, diminish the chronology of the growth of the 
Present Florida Bank even toa million years. Appalling as this 
estimate of time for building appears, it seems impossible hon- 
only rest on limitless infinities. We can indeed readily make 
an arithmetical approximation to this inconceivable total. TI 
Supply the materials. If we assume these masses at 250 feet 
thick on their northern margin in Alabama, and 1800 feet thick 
on the present southern boundary, we can safely assume an 
Average thickness of 900 feet. The length of the general line of 
oa explanation of this peculiarity is obvious on the principle already discussed— 
action of a triturating sea,” etc. : 3 
". Dana even considers the question of the transportation of the detritus ed 
ehatl 
asse ‘ones, thus originating, are not in process of formation, I venture no positive 
ie rtion on this subject, yet would express strong doubts. The fact that 
ar basaltic islands, as we recede from the reef-growing depths, lose more and 
in 
the Mate 
Case o| 
rial of the island, bears against the hypothesis. o be «9 
gx his is speci h 
eat interest to the researches above detailed by Captain Hunt, wheth 
Gite. that the formation of the reef consisted in a gradual elongation from the 
ae Without subsidence—a view also of great interest, and original—be cor- 
Not, 
It ma er / 1.93: : 
y be added here, that the possibility, not to say strong probability, of great 
gauges of level during and following the Post-tertiary, in the region of the Mexican 
48 well as in the other transverse tropical seas of the globe, the ace 
Pi and East Indian, is one among the many sources 0} that 
Problem of time connected with the Florida reef.—ys. b, D. 
ng 
the proportion of coral sand, till we finally reach a bottom of earth, like _ 
i is was found t 
