250 On the Normal Rainfall of Bengal. [No. 3, 



Seasons and causes of the Eainfall. — It has been noticed 

 above, that there is a certain amount of variation in the season of 

 maximum rainfall in eastern and western Bengal, the rains of the 

 former beginning and reaching their maximum earlier than those 

 of the latter ; but there are some other features of their periodicity 

 that may be noticed in connection with what is known of the 

 general causes that determine them. 



A glance at the tables will shew that the rainfall of Bengal is 

 far from being restricted to that period which is emphatically 

 termed ' the rains' ; in which respect, Bengal offers a marked contrast 

 to Bombay, and the western part of the Peninsular generally. 

 December is in general the driest month, but from that time for- 

 ward the monthly rainfall gradually increases, more rapidly 

 however in eastern than western Bengal, and there is no long period 

 of great siccity preceding heavy rainfall such as characterises 

 western India. 



Of the cause of the rain that falls in the winter months, I have 

 seen no satisfactory account, and our records are at present too 

 imperfect to permit of my suggesting its probable explanation. 

 The winter rains, it must be observed, are more regular and frequent 

 in Upper India than in Bengal. Generally, however, a few days 

 of rain in January and February are experienced at Calcutta. As 

 far as I have observed, this rain is preceded by a calm state of the 

 atmosphere, or sometimes by a light wind from the south, and the 

 Calcutta registers shew that it is most frequent with north and 

 east winds. The sky becomes covered with cirro-stratus which gra- 

 dually thickens, and at length resolves itself into a steady rain, less 

 heavy than the summer rains, and somewhat like the winter rains 

 of Europe. It is always followed by a considerable fall of temper- 

 ature, and generally by a cool breeze from the NW. 



As the sun advances northwards in March and April, the 

 temperature of the Peninsular rises rapidly, the focus of heat 

 being, according to the Messrs. von Schlagintweit's chart, 

 about Nagpore. With the rise of temperature, the tendency of 

 the winds becomes centripetal, the direction being between S 

 and SE along the Coromandel Coast, and W or WNW on the 

 Coast of Bombay. Herein we have the probable cause of the 



