PNEUMATICS. 301 



If we were to begin where any parallel intersects the 

 shore of the Atlantic, and draw on the map a line 

 along which the mean temperature should be con- 

 stantly the same as at the first-mentioned point, it 

 would incline greatly to the south. The point, for 

 instance, in the meridian of Petersburgh, which has 

 the same temperature with the standard belonging to 

 the parallel of that city, is about 5 south of it, or in 

 the latitude of 54 30' nearly. 



At Irkutz, latitude 52 15', longitude 105 east, the 

 mean temperature from October to April has been 

 known to be as low as 6. 8, a temperature which 

 for severity and duration exceeds any thing that has 

 yet been observed elsewhere. 



410. This increase of the severity of the winter, 

 and the consequent diminution of the mean tem- 

 perature, on going eastward, holds in all the lati- 

 tudes north of the parallel of 30 ; but the diminu- 

 tion is slower as we approach that parallel ; to the 

 south of 30 the mean heat increases on retiring 

 from the ocean. 



This diminution takes place all the way to the shores 

 of the Pacific, or very near them. The climate of 

 Pekin is vastly more severe than that of the same 

 parallel (39 54') in Europe. 



411. In all the part of the New Continent 

 which is to the north of the Tropic of Cancer, 



the 



