52 GEOLOGICAL HISTORY. [CH. 



During the succeeding phases of this period, the distri- 

 bution of land and sea was continually changing, climatic 

 conditions varied within wide limits; and in short wherever 

 Tertiary fossiliferous beds occur, we find distinct evidence of an 

 age characterised by striking activity both as regards the 

 action of dynamical as well as of organic forces. Sir Charles 

 Lyell proposed a subdivision of the strata of this period into 

 Eocene, Miocene, and Pliocene, founding his classification on 

 the percentage of recent species of molluscs contained in the 

 various sets of rocks. His divisions have been generally adopted. 

 In 1854 Prof Beyrich proposed to include another subdivi- 

 sion in the Tertiary system, and to this he gave the name 

 Oligocene. 



Occupj'ing a basin-shaped area around London and Paris 

 there are beds of Eocene sands and clays which were originally 

 deposited as continuous sheets of sediment in water at first 

 salt, afterwards brackish and to a certain extent fresh. In the 

 Hampshire cliffs and in some parts of the Isle of Wight, we have 

 other patches of these oldest Tertiary sediments. Across the 

 south of Europe, North Africa, Arabia, Persia, the Himalayas, to 

 Java and the Philippine islands, there existed in early Tertiary 

 times a wide sea connecting the Atlantic and Pacific oceans; 

 and it may be that in the Mediterranean of to-day we have a 

 remnant of this large Eocene ocean. Later in the Tertiary 

 period a similar series of beds was deposited which we now 

 refer to as the Oligocene strata; such occurs in the cliffs of 

 Headon hill in the Isle of Wight, containing bones, of croco- 

 diles, and turtles, with the relics of a rich flora preserved in 

 the delta deposits of an Oligocene river. At a still later stage 

 the British area was probably dry land, and an open sea existed 

 over the Mediterranean region. In the neighbourhood of 

 Vienna we have beds of this age represented by a succession of 

 sediments, at first marine and afterwards freshwater. Miocene 

 beds occur over a considerable area in Switzerland and the 

 Arctic regions, and they have yielded a rich harvest to palaeo- 

 botanical investigators. 



On the coast of Essex, Suffolk, Norfolk, the south of 

 Cornwall, and other districts there occur beds of shellv sand 



