The Flora of England 



rivers have silted up, and are no longer navigable, 

 as they were in A.D. I oo and much later ; and 

 parts of the country which were at that time large 

 tracts of fen or extensive morasses or marshes, 

 have been converted into good and useful land, 

 either by artificial drainage or by natural silting 

 up. At that time, also, there were immense tracts 

 of forests, which had their uses not only in the 

 production of timber, but also, like the great fens, 

 as natural defences between one tribe and another ; 

 and this abundance of large forests must have had 

 its effect on the weather and climate, producing 

 certainly a larger quantity of rain all through the 

 year. In those respects the natural features of 

 the country have been changed, and the drainage 

 of the country and the destruction of large tracts 

 of forest must have had a great effect upon the 

 rivers ; for it is certain that more rapid though 

 shorter floods are now the rule, producing the 

 further effect of deepening the rivers, and pre- 

 venting the long continuance of shallow floods 

 on the low-lying lands adjoining the river banks, 

 and in that way much lessening the cold arising 

 from constant fogs. 



These changes of the natural scenery have 

 done something to make the England of the 

 nineteenth century different from the England of 

 A.D. roo, but after all that is said, the changes 

 from this point of view, though important, are 

 not very many. It is very much the same if we 

 compare the fauna of the two periods. Some 

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