AND THEIE EXTENSION IN HEETFOEDSHIKE. 167 



The Lower Bagshot Sands, which repose on the Lonclon Clay, 

 are, in the London Basin, sterile siliceous sands and gravels, devoid 

 of fossils, forming extensive heaths and wastes in the south-west 

 of the district, and constituting the well-known Hampstead Heath 

 on the north of the Thames. In addition to this, outliers of the 

 Lower Bagshots occur at corresponding elevations at Highgate, 

 Harrow, and High Beach in Epping Forest. In the Isle of Wight 

 they are represented by the coloured sands of Alum Bay, which 

 have interbedded bands of white pipe- clay, containing dicotyledonous 

 leaves in abundance ; and these plant-remains are also found in 

 beds of the same age at Bournemouth. 



The Uppek Bagshot Beds are similarly devoid of fossils, and, 

 equally with the Lower, consist of sterile sands. They form wide- 

 spreading heaths near Sandhurst. 



But while we look in vain for the remains of animal existence in 

 these great siliceous beds, the Bracklesham: and Barton argillaceous 

 beds of the same age are filled with fossils, warning us that absence 

 of organic remains in any group of strata must not be considered 

 evidence of paucity of life at the period of deposition, but rather 

 that the conditions at a particular locality were not favourable to 

 animal Hfe, and that in other areas, where conditions were more 

 favourable, life at the time was doubtless in undiminished abundance. 



The following fossils indicate the prevailing character of the 

 Middle Eocene fauna : — Palceophis typhmts, Ototus obliquus, Valuta 

 athleta, Mitra scalera, Typhis pungens, Crassatella sulcata, Cardita 

 planicosta, Numnmlites Itevigatus. 



It may be noted here that the great limestone of the Paris Basin, 

 the NummuKtic Limestone of Egypt which yielded the blocks for 

 the Great Pyi'amid, and which extends eastwards to India and 

 even to China, is of Middle Eocene age. A very extensive sea, 

 therefore, spread its waters over the present great continental area 

 of the Old World at this epoch. The nummulites which characterize 

 the Middle Eocene are of the same class— the Foraminifera — to 

 which belong the myriads of minute organisms which almost 

 entirely make up that other oceanic deposit, the Chalk. 



At this period of the earth's history some of the greatest ranges 

 of mountains must have had no existence, since nummulites of this 

 age are found in the Pyrenees, 6,000 feet above the level of the 

 sea, and in the Himalayas as much as 16,000 feet, while both the 

 Himalayas and the Alps are partly composed of rocks of a still 

 later age. The Middle Eocenes of England by their horizontality 

 indicate clearly that this area has not partaken of the great seismic 

 movements which have elevated the great ranges of mountains just 

 named. Nevertheless, at Alum Bay we have the Chalk vertical, 

 with the Eocenes, Lower and Middle, resting against it and gi^ong 

 proof of considerable local disturbance since the Eocene epoch. The 

 lithological character of the mass of the Bagshot Beds, and the 

 flora of the argillaceous bands, alike show that the Middle Eocenes 

 of England were shallow- water deposits, probably littoral deposits of 

 the wide-spreading sea wherein the great Hmestone was being formed. 



