SECT. XXV. STABILITY OF CLIMATE. 247 



at Edinburgh the mean summer temperature is 5S'28, and that 

 of winter 38'66. Whence it appears that the difference of 

 winter temperature is much greater than that of summer. At 

 Quebec the summers are as warm as those in Paris, and grapes 

 sometimes ripen in the open air : whereas the winters are as severe 

 as in Petersburg)! ; the snow lies five feet deep for several months, 

 wheel carriages cannot be used, the ice is too hard for skating, 

 travelling is performed in sledges, and frequently on the ice of 

 the river St. Lawrence. The cold at Melville Island on the 15th 

 of January, 1820, according to Sir Edward Parry, was 55 below 

 the zero of Fahrenheit's thermometer ; and when Dr. Kane was 

 on the northern coast of Greenland it was 70 below that point ; 

 yet the summer heat during the day in these high latitudes is 

 insupportable. 



Observations tend to prove that all the climates of the earth 

 are stable, and that their vicissitudes are only periods or oscilla- 

 tions of more or less extent, which vanish in the mean annual 

 temperature of a sufficient number of years. This constancy of 

 the mean annual temperature of the different places on the sur- 

 face of the globe shows that the same quantity of heat which is 

 annually received by the earth is annually radiated into space ; 

 and that would be the case even if the quantity of heat emitted 

 by the sun should vary with his spots, for, if more were received, 

 more would be radiated. Nevertheless, a variety of causes may 

 disturb the climate of a place ; cultivation may make it wanner ; 

 but it is at the expense of some other place, which becomes 

 colder in the same proportion. There may be a succession of 

 cold summers and mild winters, but in some other country the 

 contrary takes place to effect the compensation ; wind, rain, 

 snow, fog, and the other meteoric phenomena, are the ministers 

 employed to accomplish the changes. The distribution of heat 

 may vary with a variety of circumstances; but the absolute 

 quantity lost and gained by the whole earth in the course of a 

 year, if not invariably the same, is at least periodical. 



