284 



Dr. John T. Plummer on the 



parts 



Whatev 



of these calcareous pellets, their formation was evidently extra- 

 neous to the rock which holds them, and they were deposited 



nd 



Fig. 2. 



I have critically examined great numbers of them for the purpose 

 of ascertaining their character. I conceive that waters impregna- 

 ted with carbonic acid bubbling up through beds of fragmentary 

 exuviae, have encrusted the marine particles, until some greater 

 outbreak swept them into distant regions, to be deposited with 

 other sedimentary matter, and hardened into rock : it is in refer- 

 ence to this appearance, that I have called them pisolitic balls, 

 Researches in other localities, if such exist, may finally determine 

 their true character. Fig. 2 represents a portion of this pisolitic 

 rock, which is entirely free from the usual fossils of the blue lime- 

 stone ; but in general, as already hinted, these pellets are mingled 

 with them ; and I have seen these globular masses resting in the 

 cavities of some orthoceratites, as if they had been intruded 

 into the empty shell before it was filled with the calcareous sedi- 



ment. 



Fla 



43 



Many 



ed with parallel undulations, which vary in their distance from 

 each other from half an inch to two or three inches, and rise 



perhaps 



instances half an inch 



above the level of the stone. The stratum which supplies these 

 flagstones has been traced a number of rods in one of the quarries ; 

 and throughout, the upper surface is not roughened, as other lay- 

 ers are, by imbedded fossils, but consists of a crust of sedimen- 

 tary matter, which when soft appears to have been drifted into 

 little ridges, by the ruffling of superincumbent water. 



