CLIMATES. 59 



and the mean annual temperature will then be 

 the average of all the heights of the thermometer 

 so taken for every day in the year. 



The mean annual temperature of London, thus 

 measured, is about 50 degrees and 4-10ths. The 

 frost of the year 1788 was so severe that the 

 Thames was passable on the ice ; the mean tem- 

 perature of that year was 50 degrees and 6-10ths, 

 being within a small fraction of a degree of the 

 standard. In 1796, when the greatest cold ever 

 observed in London occurred, the mean tempera- 

 ture of the year was 50 degrees and l-10th, which 

 is likewise within a fraction of a degree of the 

 standard. 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 degrees, 

 being little more than a degree below the stan- 

 dard. And in the year 1808, when the summer 

 was so hot that the temperature in London was as 

 high as 93 J degrees, the mean heat of the year 

 was 50i, which is about that of the standard. 



The same numerical indications of the con- 

 stancy of climate at the same place might be 

 collected from the records of other instruments 

 of the kind above mentioned. 



We shall, hereafter, consider some of the very 

 complex agencies by which this steadiness is pro- 

 duced ; and shall endeavour to point out inten- 

 tional adaptations to this object. But we may, in 



