30 



PHYSICAL GEOGRAPHY OF BRITAIN. 



TEMPERATURE OF THE EARTH, AT DIFFERENT ELEVATIONS, 

 IN BRITAIN. 



Temp. 



Elevation. 



Temp. 



Elevation. 



48 at yards. 



42 at 750 yards. 



47 



125 



41 



875 



46 



250 



40 



1000 



45 



875 



39 



1125 



44 



500 



38 



1250 



43 



625 



37 



1375 



The 'distribution of temperature through the seasons 

 merits the especial attention of botanists ; but in this 

 inquiry accurate observations at elevated stations are yet 

 desiderata. The maximum of atmospheric temperature 

 almost yearly occurs in July, and the minimum in Ja- 

 nuary. Either may happen a month earlier or later ; but 

 neither is ever transferred (or most rarely, if ever) to 

 spring or autumn. Springs usually attain their maxi- 

 mum in September, and minimum in February. The 

 means of the seasons, or of particular months, vary much 

 more in different years than do the annual means. Hence 

 true averages can be drawn only from observations con- 

 tinued through several years. And since the hours which 

 best represent the whole twenty-four, or the mean of the 

 extremes, also vary according to season, correct results 

 must be looked for chiefly in the data derived from re- 

 gister thermometers. In the following table the means 

 are deduced from observations for six or more years by 

 self-register thermometers ; and it may be presumed that 

 they will afford a very close approximation to accuracy. 



