44 Mr. Henry Walker's Lecture : 



of Europe tliat a more varied flora and fauna could advance. 

 But that time had not yet arrived. The humbler but not 

 insignificant herbaceous plants were the prevailing vege- 

 tation, and then began to flourish the reindeer moss, the 

 branching " cladonia" which has ever since lived on our 

 heaths and commons, reminding us to-day of the British 

 reindeer that in time found its way to the glacial Essex 

 hills. 



THE GEEAT EUEOPASIAN INVASION. 



And the time of more habitable conditions did arrive. 

 Gradually the rising land was more and more uncovered 

 by the retreating sea and the northward-shrinking glaciers. 

 Eeversions to the old Arctic weather still came on in the 

 winters, but in the summers a giant herbaceous vegetation 

 like that of Siberia established itself. Tall urnbellifers, 

 almost rivalling trees in stature during their short 

 life, and coarse but vigorous grasses made an herbaceous 

 forest and feeding ground for the future incoming herds. 

 The land continued to rise : the German Ocean, from 

 which the waters had now retreated northwards to the 

 outlying depths, became a land- valley, and the westward 

 and northward-travelling herbs and shrubs and », forest 

 trees gradually took possession. Southward, the valley 

 of the English Channel had been similarly transformed, 

 clothed with forests and open pastures, varied with mountain 

 and ravine, and perhaps chains of lakes. Far on to the 

 coast of Africa, where no Straits of Gibraltar then inter- 

 vened, the land was continuous from Britain. Favouring 

 climatal conditions were all that was wanted for the animals 

 of the north and south alternately to visit and occupy 

 each other's land. The rivers of the now united countries 

 watered a common land, those of the British area becoming 

 confluent with those of the continent ; the fresh-water 

 denizens of the one were no longer shut off by the sea from 

 inhabiting each other's waters. 



By this union of England with the Continent, the great 

 physical barrier to the rehabilitation of the long-lost and 

 long-barren land was now removed. Alternations of climate, 



