148 IV. CLIMATE. 



London and Cambridge it averages only 20 inclies. TMs 

 extreme diversity puts in contrast the humidity of the 

 hills of Mid-west Britain against the open country of 

 South-east Britain. The diversity is much less when a 

 contrast is made between eastern and western counties 

 apart from high hills. 



The rain which falls on the eastern side of the island 

 probably descends in a shorter number of hours, in pro- 

 portion to its absolute quantity, and comparatively with 

 that which falls on the western side. The atmosphere of 

 East Britain is thus comparatively less humid and less 

 cloudy than would be implied by reckoning only the 

 quantity of water, or even the number of days on which 

 rain falls. These differences affect the general vegeta- 

 tion, and perhaps to a small extent also the respective 

 floras. Plants adapted to a damp and dull climate 

 become less frequent on the eastern side of the island, 

 although they may still occur there in certain favorable 

 spots, — in swamps and marshes, near stream sides, in the 

 shade of woods, or sheltered from smi and drought in 

 narrow and humid ravines. The differences are thus not 

 so much in the species, though apparent in the general 

 vegetation. They are to be observed in the greener and 

 more luxuriant growth of many plants, and in the compa- 

 rative abundance of ferns, rushes, sedges, willows, mosses, 

 and other damp-seeking plants, on the western side. 

 Some of the species, specially adapted to a damp and 

 equable climate, are absolutely restricted to the western 

 or south-western counties, and seemingly because they 

 are destroyed by the severity of frosts on the eastern 

 side. 



The hills are more humid than the plains and other 

 low grounds. If not so by the absolute quantity of rain 

 which falls on them, they are so by the frequency of their 



