TRANSITION LIMESTOME. 15 



The limestone rocks here are differently composed, 

 but are principally of four kinds a pale gray, hard and 

 compact; a pale cream-colored, fine-grained and sono- 

 rous : these form the upper stratum of stone on our 

 down, a recent deposit, or more probably a mass heaved 

 up from its original station. The whole of this mass, 

 running nearly half a mile long, is obviously of animal 

 formation, a coral rock ; a compounded body of minute 

 cylindrical columns, the cells of the animals which con- 

 structed the material, the mouths of which are all mani- 

 fest by a magnifier. The stop in the progress of the 

 work is even visible ; soft, stony matter having arisen 

 from some of the tubes, and become indurated there in 

 a convex form ; in others the creatures have perished, 

 but their forms or moulds remain, though obscure, yet 

 sufficiently perfect to manifest the fact : these tubes, by 

 exposure to the air for any length of time, have the in- 

 ternal or softer parts decomposed, and the stone becomes 

 cellular. This stone burns to a fine white lime, and 

 is very free from impurities, containing in a hundred 

 parts 



Carbonate of lime 88 



Magnesia 8 



Silex 1 



Alumine,* colored with iron 3 



"Too 



Another quarry presents, likewise, unquestionable 

 evidence of an animal origin, veins of it being com- 

 posed of shattered parts of shells, and marine substan- 

 ces, greatly consumed and imperfect, embedded in a 

 coarse, gray, sparry compound ; an ocean deposit, not a 

 fabrication, and consequently has more impurities in its 

 substance than that of insect formation : it contains 

 about 



Carbonate of lime 73 



Magnesia 11 



Clay 14 



Silex 2 



Too 



* I have called this alumine, stained with oxide of iron ; but it 

 seems more like vegetable or animal remains, adhering to the filter 

 like a fine poaty deposit, and is lost in combustion. 



