19 
during the interval ; for over the London clay, in some parts of the 
London basin, are a series of marine sands, 600 feet thick, the 
Bagshot and Bracklesham beds, which, composing the heaths and 
plateaux of Esher, Bagshot, Purbright, Frimley, Aldershot, and 
patches showing their former extension, occur as outliers at 
Harrow, Hampstead, Highgate, and beyond Epping, in Essex. 
Beds of this age probably extended over what is now Salisbury 
plain, for it is the harder portions, remaining as isolated masses, 
which have been used in the construction of the outer circle of 
Stonehenge. At any rate, the Sarsen stones are of some 
tertiary age. (See Table at the end.) 
Prof. Ramsay alludes to the great tracts of chalk strewn with 
huge blocks of tabular sandstone, and the angular and half-rounded 
blocks which lie on the plains to the north and west of the chalk 
escarpment, marking the immense waste to which the whole 
territory has been subjected long after the close of the Eocene 
times :—‘‘ They plainly tell, in fact, that the chalk and overlying 
Eocene beds (the Woolwich and Reading and the Bagshot series) 
once spread far across the plains which the chalk escarpments 
overtook. These have been and are still being wasted back, for 
they are comparatively easily destroyed, but the strong ‘grey 
wethers’ remain, and as the rocks in which they once lay were 
slowly wasted away and disappeared, they gradually subsided to 
their present places. Besides the name of ‘ grey wethers,’ they 
are known by the name of Sarsen stones and Druid stones, and all 
the standing masses of Avebury and Stonehenge, popularly 
supposed to be Druidical temples, have been left by denudation 
not far from the spot where they have since been erected into such 
grand old monuments by an ancient race.” * 
These sandy deposits indicate a further depression of the 
sea-bed and its extension, and the existence of a southern 
land. Their fossils show conditions of considerable warmth 
in a sea still open to the south, as stated by Mr. Prestwich ; 
this sea must have extended over a considerable area, for 
these sandy beds are not only seen in the Hampshire basin, 
but their equivalents are found in the fine limestones worked 
for buildings in Paris, and in the limestones so largely used in the 
ecclesiastical edifices of southern Europe. The materials of 
which the Pharaohs constructed the pyramids were limestones 
deposited in the seas of this period, and are almost entirely com- 
posed of a peculiar foraminiferal shell, the Nummulite, and con- 
sidered, by Strabo, as the fossilized lentils such as those on which the 
workmen, who built the pyramids, subsisted. Still further east is 
this formation found, even to the Isles in the China seas, and on 
* The Physical Geology and Geography of Great Britian, London, 1874, p, 123, 
