282 The Rev. W. Buckland on the Plastic Clay Formation. 



entire thickness of some of the pits is made up of the same sands 

 and clays as on the opposite side, but more uniformly disseminated 

 through the whole mass, forming a kind of loam more like No. 12 

 than any of the other beds that have been there described ; ochre- 

 ous concretions and pyritical nodules abound in it as in No. 12. 

 The total thickness of this deposition at David's Hill above the chalk 

 is about 40 feet. Water occurs in the subjacent chalk, as soon as 

 they sink 30 feet into it. It is separated from the incumbent brick 

 earth by the bed of green sand, with the same oysters as at Cats- 

 grove. 



The whole of these beds above the chalk at Reading (those at 

 Catsgrove as well as at David's Hill) appear to be subordinate parts 

 of one formation, the next in order of succession above the chalk, 

 older than the London clay and calcaire grossier of Paris, and 

 contemporaneous with the lowest strata of the plastic clay forma- 

 tion nearest the chalk, the general history of which we propose 

 more fully to consider. 



On the north side of the town of Reading these strata do not 

 occur, being cut off by the great valley through which the Thames 

 passes, and which has been excavated to a considerable depth in 

 the subjacent chalk. But they occupy much of the ground be- 

 tween Reading and Newbury, and are seen at Hermitage, on the 

 N.E. of Newbury towards Hamstead Norris, whence a range of low 

 hills composed of them stretches eastwards towards Reading, and 

 westward to Boxford, Wickham, and the neighbourhood of Hunger- 

 ford, interrupted by vallies, which are often cut down into the sub- 

 jacent chalk. 



The breadth of this deposition on the north and south of New- 

 bury, is from Beedon Hill six miles north on the road to 

 Market llsley, to Whitway near Highclere four miles south of 



