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



Mr. Webster discovered the pure alumine ; we found however a 

 large loose block containing this substance which filled cavities and 

 veins in a mass of singular structure, composed of irregularly con- 

 centric thin layers of gypsum alternating with still thinner laminae 

 of ochreous iron ore. There were also small crystals of selenite in 

 the same cavities with the alumine. The whole mass had strong 

 marks of stalactitic origin, and was probably introduced into one of 

 the cavities on the surface of the chalk by infiltration from the in- 

 cumbent beds of marl, which abound in shells and iron pyrites, and 

 contain all the elements from which the alumine, iron, and gypsum 

 might be derived. 



In this cliff of the Castle Hill at Newhaven the following section 

 is presented, shewing beds of the plastic clay formation above the 

 chalk. 



Section of the Castle Hill at Newhaven, commencing from the 

 lowest bed. 



No. Feet 



1. Chalk, containing alumine in hollows on its surface - - 50 



2. Breccia of green sand and chalk flints, the latter covered 



with a ferruginous crust ----.----- 1 



3. Sand, varying from yellow to green and ash colour - - 20 



4. Series of clay beds containing coaly matter, selenites and 



fibrous gypsum, also leaves of plants, and sulphur- 

 coloured clay -------_-__-20 



5. Foliated blue clay containing cerithia, and cyclades, and a 



few oysters -------------10 



In this clay is a seam of iron pyrites about an inch thick 

 with pyritical casts of cyclades and cerithia. 



