56 



Featherstonhaugli's Geological Report. 



Some of the English writers have found it convenient to 

 separate the oolitic series into four divisions, placing the 

 Portland oolite and the Kimmeridge clay in the first division, 

 (descending order,) the coral rag and Oxford clay in the 

 second, the cornbrash, the forest marble, the Bradford clay, 

 the great oolite, the fuller's earth, and inferior oolite, in the 

 third, and the lias in the fourth. 



The third division, now about to be noticed, is generally 

 called the lower or Bath oolite formation, on account of the 

 beauty and value, for architectural purposes, of the freestone 

 taken from the great oolite bed near Bath. 



The inferior oolite is in some places an arenaceous deposite, 

 sometimes superimposed by limestones, with occasional oolitic 

 iron ore, and underlies a stratum of pure aluminous earth, called 

 fuller's earth. In Yorkshire this bed is ferruginous and shelly 

 in its fracture, and is subjacent to sandstones and shales, with 

 seams of bituminous coal. 



The fuller'' s earth is not a general deposite, but is found 

 very valuable in the useful arts. 



The great oolite is the distinguishing member of this divi- 

 sion, and furnishes the freestone for the public and private 

 buildings at Bath, in England, as well as in Normandy and 

 other parts of the continent. 



The Bradford clay is a partial deposite, remarkable for its 

 very perfect specimens of apiocrinites rotundus, or the round, 

 pear-shaped encrinite. 



The forest marble is a coarse, shelly, oolitic limestone, as- 

 sociated with sands and sandy accretions. It is a remarkable 

 bed in the geological history of the series for having produced 

 the first specimen of a quadruped, the didelphis bucklandi, 

 an extinct species of opossum. 



The cornbrash is a coarse, shelly limestone, owing its some- 

 what dissonant name to the facility with which it disintegrates 

 and yields to the plough, being, according to the old provin- 

 cial term, brashy or breaky enough to enable the plough to 



