18 



THE BRITISH ISLES. 



In summer, when the temperature of the air is higher than that of the ocean, 

 the latter exercises a moderating: influence upon the degree of heat, more especially 

 in the west. Only in the inland counties and on part of the east coast do we meet 

 with features reminding us of a continental climate. The temperature during 

 that season decreases with a considerable degree of uniformity from 63° Fahr., in 

 the Thames valley, to 54^ in the Orkneys, and the isothermals run across the 

 country from east to west. 



Very different are the climatic conditions of winter, for it is then that the tepid 

 waters of the Atlantic, by considerably raising the temperature of the air, exercise 



Fig. 11.— Isothermal Lines for July and January. 

 According to Alexander Buchan. 



'5»WoPC<r 



Temperature of Jiilj-. 



Tempera tuie of Januaiy. 



more powerfully their beneficent influence. The isothermal lines, instead of turn- 

 ing east and west, then almost follow the direction of the meridians, and the mean 

 temperature of the Orkney Islands is hardly inferior to that of London, situated 

 over 500 miles to the south. In the eastern part of Great Britain, and more 

 especially in that portion of it which lies between the Naze and the Firth of Forth, 

 the winter is coldest, owing to the greater exposure to easterly winds blowing from 

 the ice-clad plains of the continent, as well as to the lower temperature of the 

 German Ocean,* whilst the warm westerly winds are shut out by meridional 



* Temperature of the Atlantic in Januarj-, on the north--west coast of Scotland, 4-5° Fahr., or 5° 

 wanner than the air. Temperature of the northern part of the German Ocean, 41°, or 2' warmer than 

 the air. 



