1 870.] On the Normal Rainfall of Bengal. 257 



those at lower elevations in similar circumstances of exposure, but 

 the evidence is insufficient to shew whether this is the elevation of 

 maximum precipitation, and there are other circumstances of posi- 

 tion, apart from the character of the prevalent rain-bearing wind, 

 at least equally influential in determining the amount of pre- 

 cipitation. 



To sum up the principal facts educed in this discussion. 



The rainfall of Eastern Bengal commences at an earlier period 

 and is on the whole heavier than in "Western Bengal at stations 

 equally distant from the sea, and at equal elevations. 



The SW monsoon of Eastern Bengal is probably due to the 

 low pressure in Central Tibet, towards which the saturated air 

 from the Bay flows as a SW wind, traversing the hill plateau 

 between Assam and Cachar in its course towards upper Assam, 

 where the barrier of the Himalaya ceases and allows it a passage to 

 the north. The corresponding monsoon of Western Bengal tends 

 on the contrary towards the heated plains of the Punjaub, access 

 to Central Asia being barred by the Himalaya range. 



Besides the regular rains of the SW monsoon, Western Bengal 

 receives a small precipitation in the cold weather months, similar 

 to the water rains of Central and Upper India, but less in quantity 

 and regularity. It also receives spring rains, irregular in quantity 

 and period of occurrence, which are probably due to an inflow of 

 moist air from the Bay towards Central India, the temperature of 

 which is then normally higher than that of any other part of the 

 Peninsular. The autumn rains of Madras are felt in Orissa as a 

 slight prolongation of the regular rains. 



