1818.] Distribution of Heat over the Globe. 183 



a few months are warmer than in the latter ; as, for example, the 

 heats in Madras are greater than those in Cumana. In the tem 

 perate zone it has been long known that the cold of the winter 

 augments in a more rapid progression than the heat of the 

 summer decreases ; it is also known that the climate of islands, 

 and the sea-coast, is milder than the interior of continents ; it is, 

 therefore, an important object to compare the mean temperatures 

 of the three winter and the three summer months, at different 

 latitudes, and to observe how the curves of the isothermal lines 

 modify these relations. By comparing together a tract on the 

 west with one on the east side of the Atlantic, extending across 

 the different isothermal lines, we find that the difference between 

 the two seasons increases more in the transatlantic than in the 

 cisatlantic district. But in both the districts the division of 

 the temperature between the winter and summer months is such, 

 that upon the line of 32° the difference is nearly double what it 

 is upon the line of 68°. 



In tracing the same isothermal line from west to east, in order 

 to observe the difference between the winters and the summers, 

 we find that the difference is less near the convex summits of the 

 lines than near the concave summits. The same causes which 

 tend to raise up the lines towards the pole also tend to equalize 

 the seasons. Europe may be regarded altogether as the western 

 part of a great continent, and subject to all those influences 

 which make the western sides of all continents warmer than the 

 eastern. The same difference that we observe in the two sides 

 of the Atlantic exists on the two sides of the Pacific ; in the 

 north of China the extremes of the seasons are much more felt 

 than in the same latitudes in New California, and at the mouth of 

 the Columbia. On the eastern side of North America we have 

 the same extremes as in China ; New York has the summer of 

 Rome and the winter of Copenhagen ; Quebec has the summer 

 of Paris and the winter of Petersburgh. And, in the same way 

 in Pekin, which has the mean temperature of Britain, the heats 

 of summer are greater than those at Cairo, and the cold of winter 

 as severe as that at Upsal. This analogy between the eastern 

 coasts of Asia and of America sufficiently proves that the ine- 

 qualities of the seasons depend upon the prolongation and 

 enlargement of the continents towards the pole, and upon the 

 frequency of the N.W. winds, and not upon the proximity of any 

 elevated tracts of country. ' / 



