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THE WONDERS OF GEOLOGY. Lect. III. 



masses of the metamorphic, Cambrian, and Silurian rocks. 

 These are succeeded by a band of the carboniferous and 

 triassic strata, with a few intrusions of metamorphic and 

 plutonic rocks, that stretches from the coast of Devonshire, 

 through the midland counties by Leicestershire and Derby- 

 shire, to Newcastle. On the south-east of this tract the 

 oolitic and cretaceous formations, chiefly made up of argil- 

 laceous and calcareous deposits, constitute a diversified 

 agricultural district, which extends from the southern 

 shores of Dorset and Hants, to the coast of Yorkshire. The 

 Wealden is exposed in the area between the ranges of the 

 north and south downs of Kent and Sussex. The Ter- 

 tiary overlie the uppermost secondary strata ; they occupy 

 the eastern and south-eastern maritime districts, and form 

 the area on which stands the metropolis of England ; they 

 are covered in many places by the drift and alluvial 

 debris, which contain mammalian remains. 



After this comprehensive view of the leading characters 

 of the principal rocks and strata of which the present 

 islands and continents are composed, we proceed to a more 

 particular examination of the several formations in their 

 natural sequence, or order of superposition. 



9. Drift and alluvium of the modern epoch. — 

 When explaining, in the previous Lecture, the circum- 

 stances under which the remains of terrestrial quadrupeds 

 occur in the superficial deposits, the nature and origin of 

 those beds were briefly described. It is necessary, in this 

 place, to offer a few remarks on the phenomena presented 

 by the drift and other alluvial accumulations of the 

 modern epoch. 



The drift and alluvium consist of beds of loam, sand, and 

 gravel, variously distributed; being, in some instances, spread 

 over extensive areas ; in others, forming mounds, ridges, 

 and hills of low elevation ; in others cresting the summits 

 of abrupt and lofty escarpments: sometimes radiating, as it 



