The Rev. W. Buck land on the Plastic Clay Formation. 299 



sandy, and blackish. The sand dividing them is also said to vary- 

 in colour like the plastic clay itself, from white, grey, and yellow, to 

 grey mixed with red and pure red. The English beds of plastic clay 

 and the sands attending them at Reading, Corfe Castle, and Alum 

 Bay, exhibit analogous variations in colour and consistency ; indeed 

 at the latter place they run through almost every possible combina- 

 tion in the scale of colours. Between the upper plastic clay and 

 calcaire grossier of Paris, there is also stated to be sometimes found 

 a bed of sand of irregular thickness, which they are doubtful whe- 

 ther to consider as belonging to the formation of plastic clay or cal- 

 caire grossier, but are rather inclined to attribute it to the former. 

 It contains organic remains in very few places. Is it not improbable 

 that this bed is contemporaneous with some of the upper strata of 

 the plastic clay formation which we find at Loam Pit Hill, at Black- 

 heath, and in the Isle of Wight, at which last place the beds belong- 

 ing to this series are accumulated to a thickness far greater than has 

 been yet noticed in any other spot, amounting at Alum Bay, ac- 

 cording to Mr. Webster, to 1131 feet, interposed between the chalk 

 and London clay. 



Viewing it on the great scale then we may consider this formation, 

 which has been characterized by the title of plastic clay, as com- 

 posed of an indefinite number of sand, clay, and pebble beds, irregu- 

 larly alternating. Of these, the sand forms in England, the most 

 extensive deposition, in which the clay and pebbles are interposed 

 subordinately and at irregular intervals. 



Again, the occurrence of organic remains in the different beds of 

 this formation, is like the alternation of the strata composing it, ex- 

 ceedingly irregular : sometimes they occupy the clay, at other times 

 the sand or pebbles, and very frequently are wanting in them all. 



A good example of shells occurring, mixed with large pebbles, 



