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 
100 
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 
100 
* 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 peaty deposit, and is lost in combustion. 
