A GRASP OF GEOLOGIC TIME. 167 



also was connected with the British islands. Most of the 

 Baltic Sea constituted a great lake. The land had even 

 a greater northern extent. Continental Europe stretched 

 to Spitzbergen, Iceland and Greenland, and now, as the 

 climate was genial, European types of plants and animals 

 ranged to those far northern shores. The Rhine and the 

 Weser discharged into the ocean in the latitude of the 

 FarOe islands ; the Thames, the Great Ouse, the Humber, 

 the Tyne, the Tweed and the Dee were all tributaries of 

 the Rhine. At this epoch man found his way into Great 

 Britain. This was the period immediately following the 

 dissolution of the continental glaciers. It was succeeded 

 by a subsidence and a colder, humid climate. Great 

 Britain became insular. Marshes and bogs prevailed 

 throughout northern Europe. Another elevation was at- 

 tended by the return of a milder climate and a luxuri- 

 ant growth of forests. Bronze found its way into Great 

 Britain. Then still another subsidence occurred, and a 

 period of wet weather. Iron was introduced. Thus with 

 increasing dryness of climate prehistoric times passed into 

 historic.* 



It may be that northern Europe has not experienced 

 so great a number of oscillations in Post-Tertiary times; 

 but all geologists are agreed that since the beginning of 

 the Glacial Age Great Britain has been twice continental 

 and twice insular. It is generally agreed also that within 

 the same interval the North Sea has been dry land. That 

 Greenland, Iceland and Spitzbergen have been joined to 

 Europe is a firm doctrine of science, and the only ques- 

 tion is whether the connection occurred in Post-Tertiary 

 time or earlier. In any event, most of the great changes 



* J. Geikie, Prehistoric Europe, ch. xiv, xxi and xxii. 



