1890.] NATURAL SCIENCES OF I'HILADELi'lI JA. 315 



the rate ot'i'o inch per anuuiii, which hin' been assumed by Irvine,' 

 would Yield in this^ period of time a depth of water no greater than 

 actually exists on some of the reefs to-day, about two or three feet.'- 

 But theu it should not be forgotten that the three centuries repre.sent 

 merely the least time for which we have a record of the completion of 

 a single reef; the identical condition of stability may have existed 

 for centuries before, and certainly a long period was consumed in 

 the growth of the reef before it reached the surface. Surely some 

 decided evidence of solvent action, in the form of a true basin-struc- 

 ture, might have been expected in this time ; and the more if we 

 further take into account peripheral acceleration. But such 

 evidence is clearly wanting. So little, however, is as yet known 

 regarding the amount and capabilities of solution that, perhaps, too 

 much stress should not be laid upon this negative evidence — espec- 

 ially, as we seem to be dealing with a somewhat mysterious force, 

 whose woi'kings are, at least to me, a little inscrutable. The solvent 

 " power" that permits to build up and then, apparently without 

 cause, suddenly reverses and begins to remove, is possessed of a 



Mr. Agassiz, in a note to Prof. Shaler's paper, seems to think that tlie Florida 

 Everglades may be largely of a reef formation, or to be due to sedimental accu- 

 mulation behind and between reefs. This is a revival in part of the old reef-theory 

 of growth of the Floridian peninsula, which recent researches have abundantly 

 disproved. Mr. Agassiz recognized that this theory is no longer tenable, but he 

 manifestly lays loo much stress upon the probability of a like structure holding 

 good for that part of the peninsula which lies south of the " northern extremity,"' 

 or even for that which is mainly comprised within the region of the Everglades 

 itself. My own researches, which have since been supplemented by those of Dr. 

 Dall, show that heavy fossiliferous deposits of Pliocene age are found nearly half 

 across the peninsula on the Caloosahatchie, and their position there makes it prac- 

 tically certain that they largely underlie the region of the Everglades. 1 have so 

 stated it in my report (p. 6.5) : " The evidence, further, is very strong that beyond 

 Lake Okeechobee and the Caloosahatchie the structure of the State is for the mo^-t 

 part identical with that above it, and the observed facts clearly prove that this cor- 

 respondence must exist over at least a considerable portion of the unexplored re- 

 gion of the Everglades." Mr. Agas-;iz ha-; apparently not read my report (beyond 

 possibly the opening sentence), otherwise he could hardly have stnted (p. lo7l that 

 my "explorations were limited to the portions of the west coast of Florida included 

 between Cedar Keys and Punta Rassa, and did not touch the Everglade district."' 



1 Nature, March 1.5, 1888; this point is discussed in my " Bermuda Islands," 

 pp. 203-205, 1889. 



- It has already been remarked that the central reef-depression is in most 

 cases merely a negative one, a rim having been formed through up-throws by the 

 beating waters. 



