THE NON-LIVING WORLD 1^9 



between the north-east and south-west of England. To 

 the upper portion of the Jurassic rocks belong the 

 Solenhofen slates of Bavaria. The Cretaceous and Neo- 

 comian systems include the Wealden, the lower and upper 

 Gault, and the Chalk. The Wealden is well seen in the 

 Greensand, the south-east of England, where (in Kent, 

 Surrey, Sussex, and the Isle of Wight) it is considered to 

 represent the delta of a large ancient river. The Chalk 

 formation ranges from Lyme Regis to Flamborough 

 Head, and also forms both our North and South 

 Downs. It and the Maestricht beds terminate the series 

 of Mesozoic formations, and a great break exists between 

 it and the Tertiary formations which follow. The break 

 between them seems to be partially bridged over in 

 North- Western America by certain beds known as the 

 " Lignite Series." The Cainozoic, or Tertiary rocks 

 consist of three systems the Eocene, the Miocene, 

 and the Pleiocene. Eocene rocks underlie both Paris 

 and London, and form very important deposits in 

 North America, The Miocene formation is widely 

 distributed in Europe and the North American Con- 

 tinent, but is very slightly represented in Britain. 

 The igneous rocks which form the Giant's Causeway, 

 the Island of Staffa, of Mull and others, belong, how- 

 ever, to the group. The Pleiocene formation is exten- 

 sively distributed in Europe, Asia, and the United 

 States. In England it is represented by the Nor- 

 folk and Suffolk "Crag." The later, Pleistocene, rocks 

 the so-called Quaternary strata include the deposits 

 found in ancient caves in Europe and those thrown down 

 during what is known as the Glacial Epoch. That such 

 a period of intense cold prevailed over Northern and 

 Central Europe and the greater part of North America, 

 in geologically recent times, is shown by the evidence of 



