350 ACCOUNT OF THE ARCTIC REGIONS. 



the more interesting and striking, the more it is in- 

 vestigated. 



When we experience particularly cold winters, 

 or particularly hot summers, we might suppose that 

 the mean temperature of the years in which the for- 

 mer occur, would he greatly below, and that of the 

 years in which the hot summers occur, would be great- 

 ly above the general standard. But this will seldom 

 be found to be the case *. For here the causes, 

 whatever they may be, which tend to produce the 

 equilibrium, exert their influence, and compensate 

 for the disarrangement, by :ni extraordinary supply 

 or abstraction of heat, whereby the general mean is 

 still preserved nearly uniform. Hence in temperate 

 climates of the northern hemisphere, the mean tem- 

 peratiu'e of any one year, derived from the mean of 

 the daily extremes of heat and cold, or from any 

 particular number of daily observations, continued 



" When the frost was so severe in London, that the Thames 

 was passable on the ice, in 1788, the mean temperature of the 

 year was 50°.6, being within a small fraction of a degree of the 

 standard ; and in 1796, when the greatest cold ever observed in 

 London occurred, the mean temperature of the year was 50°.l, 

 which is likewise within a small fraction of a degree of the 

 standard temperature. In the severe winter of 1813,-14, when 

 the Thames, Tyne, and other large rivers in England were 

 completely frozen over, the mean temperature of the two years 

 was 49*, being a little more than a degree below the standard. 

 And in the year 1808, when the summer was so hot that the 

 temperature in London was as high as 93'. 5, the mean heat of 

 the vear was 50'.5, which is about that of the standard. 



