164 J. L. LOBLEY THE EOCENES OF ENGLAND 



causing a great flow of warm water from the tropics to the north- 

 western coasts of Europe, and which great body of warm water 

 warms and renders humid the winds which blow over it during so 

 many days in the year from the south-west. This will indicate 

 how we may account for the various climatal conditions of the 

 Eocene Epoch, though the hypothesis of an alteration of the in- 

 clination of the earth's axis has been called in to explain the 

 great changes of temperature wliich have occurred during the later 

 geological periods. If then we suppose the small and shallow 

 Thanet Sands sea to have been closed to the south and open to 

 the north, open to the influx of the cold polar waters, we shall 

 have conditions that will sufiice to give a sea of such a temperature 

 as to be favourable to the life and development of the genera 

 represented in these beds. 



The Woolwich and Reading Seeies. — A series of deposits of 

 great interest overlies and overlaps the Thanet Sands, for the 

 "Woolwich and Reading Series has a much gi-eater extension in 

 England than the underlying formation, which terminates west- 

 ward between London and Windsor, and is little seen north of the 

 Thames. Nor are the Woolwich beds confined to the London 

 Basin, for in the Isle of Wight they are seen resting against the 

 upheaved Chalk. The fauna and the flora of these beds clearly 

 indicate that the deposition took place during a period in which 

 several alterations in the relative level of land and water took place, 

 — alterations which at one time gave a river, at another an estuary, 

 and at another an open sea over the same area ; for freshwater, 

 estuarine, and marine shells alternate in the various beds composing 

 the Woolwich and Reading Series. 



In the extreme west — the Isle of Wight— the Woolwich Beds, 

 consisting of clays of mottled colours, and called fi'om their 

 consistence the " Plastic Clay," are quite devoid of fossils. In the 

 neighbourhood of Reading argillaceous beds prevail, with oysters 

 in abundance, while in the eastern part of the London Basin the 

 beds vary greatly in character, and yield many species of ]Mollusca, 

 including some river shells, and, in addition, an assemblage of plant- 

 remains, which also tell us of the proximity of land. Perhaps the 

 most marked feature of the Woolwich and Reading Series is the 

 occurrence of beds almost entirely composed of shells. These beds 

 contain, in some instances, shells of Cyrena mingled with those of 

 oysters, but in others the cyrenas arc free from intermingled 

 oysters, and in others again the oysters are free from cyrenas. 

 The thickness of the formation in the London Basin is about eighty 

 feet, and in the Isle of Wight, where the beds are nearly vertical, 

 it is 160 feet thick. 



Among the fossils the following are the best-known : — Mollusca : 

 Melania inquinata, l\dudina lcn(<t, ('I'ritJiiioii ftotatuni, Ci/rena 

 cuneiformis, C. dcpcrdita, Odrca JJellovacina, 0. tencra. Plants : 

 Bryandroides Preskvichii, Ficus Forbesi, Lmirus Ilookeri. 



The Oldhaven Beds. — The shell beds and clays of the Woolwich 

 Series give place in Keut to pebble-beds of great thickness, which 



