386 SCIENCE FROM AN EASY CHAIR 



in the Thames and Severn in those days, and left 

 its bones and teeth in the older gravels of those and 

 other European rivers, where we now find them. The big 

 almond-shaped and leaf-shaped flint implements of the 

 English (Fig. 73) and French gravels (Fig. 74) belong 

 to this period. We have no knowledge whatever of the 

 men who made them. 1 The mammoth was not there, 

 but another species of elephant (E. antiquus) and a 

 peculiar rhinoceros (R. merckii). The deepest and oldest 

 deposits in some caves belong to this age, as well as the 

 high-lying gravels of St. Acheuil, of many English river- 

 valleys, and of Chelles on the Seine. This period is not 

 represented by much deposit in caves, though some 

 caves contain very deep-lying layers enclosing bones or 

 teeth of the animals characterising this period. 



Older than the Age of the Hippopotamus are de- 

 posits which are reckoned by geologists as " Pliocene " 

 no longer Pleistocene and are called " Tertiary," not 

 " Quaternary." The forest bed of Norfolk (regarded by 

 Professor Marcelin Boule as of transitional character, as 

 shown in the tabular view on p. 384 bis}, the Norwich 

 crag, the Suffolk red and coralline crag, and very ex- 

 tensive sandy deposits all over Europe belong to the 

 Pliocene. The earliest or first great extension of glaciers 

 occurred late in this period. The animals are very 

 different from those of the Pleistocene ; the great mastodon 

 and the tapir are there, and the sabre-toothed tiger. 

 Implements manufactured by man are found in the 

 oldest Pleistocene, and there is no reason to doubt that 

 we shall find his workmanship in the Pliocene, too, 

 though it is not admitted that this has yet been done. 

 It is a question still eagerly studied and debated as 

 to whether the roughly chipped flints found in gravels 

 on high downs in the south of England, and called 

 1 See, however, farther on as to the lower jaw found at Heidelberg. 



