104 UPPER SECONDARY ROCKS. 



Above the lias clay we have what is called the 



Cheltenham or inferior oolite, which in some places 

 is an arenaceous deposite, sometimes consisting of 

 nearly equal divisions of soft oolite and slightly cal- 

 careous sand, with occasional oolitic iron ore : over 

 this, in some places, is a peculiar kind of clay, called 

 Fuller's earth, valuable in the useful arts ; occasion-' 

 ally it forms beds 150 feet in thickness. Above 

 this comes a slaty calcareous limestone, called Stones* 

 field slate, remarkable for its organic remains ; and 

 next in order is the great oolite, which contains the 

 best and largest beds of building stone, called Free- 

 stone. Many of the handsomest houses in Bath 

 (England) are built of this stone. As we ascend 

 we next meet with what is called Forest marble, 

 containing argillaceous deposites, termed Bradford 

 clay. Next we find a coarse, shelly limestone, 

 called Combrash* full of fossil remains. The above 

 deposites form what may be called the second divis- 

 ion of the oolitic series in the ascending order. 

 The third division embraces the Oxford clay, the co- 

 ral rag, calcareous sandstone and freestone, and Kim- 

 mendge clay. The upper and last division of oolite 

 consists of Portland sand and Portland stone. The 

 latter is of a yellowish white colour, and forms a 

 very fine building stone. The average thickness 

 of the deposites in each of the above divisions is 

 500 feet, making 1500 feet for the whole ; none of 

 which are known to exist in the United States. A 

 great variety of fossil remains are found in the se- 

 ries, especially in the Stonesfield slate, such as 

 those of the megalosaurus or gigantic lizard, which 

 was forty feet in length and twelve feet high ; also 

 of birds, and animals of the opossum genus, and of 



* This word derives its name from the facility with which 

 it disintegrates and yields to the plough ; being, according to a 

 provincial term, brashy or breaky enough to enable the plough 

 to prepare the surface where it prevails for wheat, which is al- 

 ways called corn in England. 



