63 Remarks upon East Florida. 



closely joined, like that superimposed. A thin stratum of sand 

 next succeeds ; and then a third stratum of shelly rock, about 

 two feet and a half thick, the component parts of which are in a 

 state rather more comminuted than any lying above. This stra- 

 tum is likewise of a more solid and uniform character than its as- 

 sociates, and gives the largest blocks for building purposes. A 

 sandy stratum is found below this, and, so far as an examination 

 has penetrated, the coquina formation descends no lower. 



All these strata are firm concretions, their component parts being 

 obviously conglutinated by a calcareous substance, which holds 

 them well together. This foreign substance, or cement, is quite 

 visible in the finer formations, though little seen in the coarser. 

 Taking up a piece of the latter, the cause of cohesion is appa- 

 rently so slight, that one is surprised that the mass does not crum- 

 ble at a touch. 



It is a common conjecture that the coquina is of recent forma- 

 tion, and that causes are still operating to produce it. This 

 conjecture has some apparent and plausible grounds. It Wants, 

 however, the support of deeper investigation into the character 

 and force of these causes. Fragments have been constantly 

 heaping up on the coast, portions of which have been long lying 

 in a quiescent state, without exhibiting any evidences of a change, 

 or a tendency to one, particularly of a change from a loose to a 

 concrete state. The upper stratum of the quarries we have been 

 describing, would be likely to assume the character of the strata 

 below, if such a change were in progress. But the century du- 

 ring which it has been subject to observation, has witnessed no 

 alteration. The fragments all lie in a separated state, without 

 showing any signs of cohesion. 



It has been surmised, that the animal matter of the shells 

 might have furnished the element of cohesion. But this surmise 

 would seem to be at once disproved by the condition in which the 

 shells were found, when the concretion took place. It is evident 

 that they must have been subjected to a long and severe process 

 of attrition and contusion, previous to that event ; such a process 

 as must have widely separated all animal matter, from its former 

 covering. Besides, there is no reason for supposing, that this an- 

 imal matter, even if it had existed in connection with the shells at 

 the time the rocky formation occurred, could have produced the 

 effect assigned to it. 



