ELISHA MITCHELL SCIENTIFIC SOCIETY. 89 



<of stream. It is a compact, whitish eocene Umestone, with frag- 

 ments and shell prints. 



Near Bartow the rock, as exposed in ravines, gullies and springs 

 is generally soft, light, cellular, whitish; while in places it is com- 

 pact, fragmentary conglomerate, containing iron sand. Rock near 

 Bartow is used in building of chimneys, &c. 



At Fort Meade rock is to be found in bed of Peace creek, and on 

 right bank is exposed in high bluff of 30 to 40 feet above water level. 

 It is a dull white calcareous agglomeration of rounded (or ovoid) 

 gravel, particles one-tenth to one-half and occasionally one inch long 

 by one-quarter inch shorter diameter, white and compact, with 

 small sharks teeth, worn fragments of shells, spines of echini and 

 bits of bone. This resembles quite closely the phosp' atic conglom- 

 erate of Alefia river. Above this calcareous rock occurs a sandy 

 calcareous loam, with gravel and angular fragments of the calca- 

 reous rock three to four feet thick. 



At several places along the west shore of Hillsboro Bay, as near 

 mouth of Alefia river, the water is encroaching upon the land, as 

 can be seen by the fact that the banks are low and trees are now to 

 be seen growing out beyond the high land in the region now partly 

 flooded with salt water, showing probably that a subsidence of the 

 coast is now in progress. And there is additional evidence of this 

 in the fact that near rhe mouth of this and other streams, the eocene 

 limestone rock in the beds of the streams has been eroded out to a 

 depth below which any erosion appears to be going on at present 

 time. When the coast was more elevated than now, these channels 

 were worn out by action of river water. 



The fact, however, that the post pliocene marl deposits lie on 

 top of the eocene lime rock, in depressions worn out by action of 

 water, goes to show that at a time prior to the deposition of these 

 patches of marl, the level of this eroded surface must have been 

 lower than at present; and at time these deposits were made the 

 surface must have been of course below tide level. 



The conclusions which the writer draws from the facts brought 

 out by these observations, are: (1), the limestone rock underlying 

 the region of country about Tampa belongs to the upper eocene as 

 already pointed out by Conrad & Toumey. And as a gentleman of 

 intelligence who visited Fort Myers, informed the writer, that the 

 rock at that place was both in appearance and in fossils, similar to 

 that about Tampa, the eocene limestone rock almost certainly ex- 

 tends at least as far south as that point. (2.) In order to have pro- 

 duced the existing condition of affairs about Tampa Bay, an erosion 



