18980 



on a Yorkshire Moor. 



635 



found in the Pyrenees), Narthecium ossifragum and Aira flexuosa 

 have disappeared. 



A favourite explanation rests upon the changes of climate to 

 which the glaciation of the northern hemisphere bears emphatic 

 witness. When the plains of Northern Europe were being strewn 

 with travelled boulders, when Norway, Scotland and Canada were 

 covered with moving ice, the vegetation of Siberia and Greenland 

 may well have extended as far south as Switzerland. 



I do not doubt the general truth of what we are taught respecting 

 the glacial period, but I think that we are apt to explain too much 

 by its help. We know very little 

 for certain as to its effect upon 

 vegetation. Our information con» 

 cerning the prcglacial flora is ex- 

 tremely meagre, nor are we in a 

 230sition to say positively what 

 sort of flora covered the plains of 

 Europe after the severity of glacial 

 cold had passed away, and before 

 men had changed the face of the 

 land by tillage.* We know rather 

 more about the animals of these 

 ages, for animals leave more recog- 

 nisable remains than plants, but 

 the indications of date, even in the 

 case of animals, are apt to be slight 

 and uncertain. On the whole, 1 

 doubt whether the glac'al period 

 marks any great and lasting change 

 in the life of the northern hemi- 

 sphere, f I think it probable that 

 since the glacial period passed 



away, the countries of Central . 



ifcurope posses.sed many species, both of plants and nnimals, which we 

 should now consider to be Arctic, and that these Arctic species endured 

 until many of them were driven out by an agent of which geologists 

 usually take little notice. I shall come back to this point. 



'I'he animal life of tlie Yorkshire moors is not abundant. Hares, 

 shrews, stoats, weasels and other small quadrupeds, which are 

 plentiful on the rough pastures, cease whei-e the heather begins. 

 There are a good many birds, some of which, like the grouse, the 



Fig. 12. — Transverse se(;tion of leaf of 

 Feshica ovina. In tliick sections 

 hairs are seen to point iuwafdg 

 from the inner epidermis. 



* Some information has been gained by investigation of plant reniains found 

 beneath the bogs of Denmark, and beneath the palseolithic brick-earth at 

 Hoxne. 



t It is well known that this position has been strongly maintained by Professor 

 Boyd Dawkins ("Early Man in Britain," p. 123,&c. ' Q. J. Geol. Soc' vol. xxxv. 

 p. 727, and vol. xxxvi. p. 391>). On the other side. Dr. James Geikie may be 

 consulted ('Prehistoric Europe,' ch. iii, &n.). 



