330 



AVERAGE RAINFALL 



[Ch. XV. 



near the shores of the Baltic, lat. 60° N., is nearly 16 inches 

 while at Bergen on the Atlantic coast, in the same lat. and 

 only 440 miles distant, the fall, according to Professor Forbes 

 is 77 inches. This difference arises from the position of 



shore of the ocean where the prevailing 



their moisture before crossing 

 Sweden, on their way to the borders of the 



Bergen on the 



westerly winds discharge 



Winds blowing from the sea are generally surcharged 



Norway 

 Baltic. 



with moisture, while those blowing from the land are com- 

 paratively dry, and it is almost everywhere found that the 

 quantity of rain diminishes as we proceed from the borders 



In India, 



of the ocean into the interior of continents. 

 Colonel Sykes found by observations made in 1847 and 1848, 

 that at places situated between 17° and 18° north lat., on a 

 line drawn across the Western Ghauts in the Deccan, the 



fall of rain varied from 21 to 219 inches.* The annual 

 average in Bengal is probably below 80 inches, yet Dr. Joseph 

 Hooker witnessed at Chirapoonjee, in the year 1850, a fall of 

 30 inches in 24 hours, and in the same place during a re- 



November) 



This occurred on the south face of the 



or Garrow) 



XIX 



the depth during the whole 



of the same year probably ex- 

 ceeded 600 inches. So extraordinary a discharge of water 

 is very local, as will presently be seen, and may be thus ac- 

 counted for. Warm, southerly winds, blowing over the Bay 



during their 



of Bengal, and becoming laden with vapour 

 passage, reach the low level delta of the Granges and Brah- 

 mapootra, where the ordinary heat exceeds that of the sea, 

 and where evaporation is constantly going on from countless 



marshes and the arms of the great rivers. 



A mingling of 



two masses of damp air of different temperatures probably 

 causes the fall of 70 or 80 inches of rain, which takes place 

 on the plains. The monsoon having crossed the delta, im- 

 pinges on the Khasia Mountains, which rise abruptly from 

 the plain to a mean elevation of between 4,000 and 5,000 

 feet. Here the wind not only encounters the cold air of the 



mountains, but. what is fir morft effective as a, refrifferatina' 



* Phil. Trans. 1850, p. 354 





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