1873.] H. F. BTanford— On the Climate of Bengal. 179 



ed also twice, viz., in January 1860 and 1861, and 52-8° has been observed 

 twice, viz., in January 1857 and 1861. The extreme absolute range of the 

 temperature of the Capital is therefore a little over 53°, and the mean tem- 

 peratures of December and May are 68-5° and 85° respectively. The annual 

 rise and fall of temperature exhibits some other local variations. Thus in 

 Orissa and the Western part of the Gangetic Delta, December is the coldest 

 month of the year ; elsewhere the temperature reaches its minimum in Janu- 

 ary. This difference is due to the sea-winds setting in on this part of the 

 coast very early in the year ; whereas on the Arakan coast and in Bihar, 

 their influence is not felt till much later in the season. 



May is the hottest month of the year in all parts of the Lower Provinces 

 with the exception of a part of Bihar, Asam and Kachar. In the former, the 

 average temperature of June is a little above that of May ; and in the latter 

 districts, which enjoy a comparatively cool but humid atmosphere in April 

 and May, the temperature rises slowly and uniformly up to July or August. 

 In upper Asam it is higher than in the lower part of that province, from 

 May to October ; and higher also than in Kachar. The mean temperature of 

 Sibsagar in July and August is 81'7,° that of Goalparah 8T2°, and that 

 of Silchar 82.° 



During the rains, the temperature of the Hazaribagh plateau, to the 

 West of the Delta, falls more rapidly than that of any other part of Bengal. 

 Between May and October, the fall at Hazaribagh is rather more than 

 11° ; while at Barhampur, under about the same latitude, it is only 4>^° ; at 

 Calcutta little more than 3°, and even at Patna it does not exceed 8°. This 

 peculiarity appears to be due principally to the cloudiness of the plateau in 

 the daytime, whereby the sun's heat is rendered less intense ; and to the 

 greater radiation at night. This fact has an important bearing on the value 

 of Hazaribagh as a station for European troops, and as a sanitarium For 

 invalids from the plains. 



The high humidity of the atmosphere in Bengal, and more especially 

 in its Eastern districts, has become proverbial ; and if the term be used in 

 reference to the quantity of vapour in the air, as measured by its tension, the 

 popular belief is justified by observation. But if used in the more usual 

 sense of Relative Humidity, that is, as referring to the percentage of vaoour 

 in the air, in proportion to that which would saturate it, the average annual 

 humidity of a large part of Bengal is considerably lower than that of England. 

 In illustration of this, I give a comparative table of the mean vapour tension 

 and relative humidity of London and Calcutta in each month of the year 

 and the mean of the whole year ; the data for the former place beino- taken 

 from an Essay on the Climate of London by the late Professor Daniell • those 

 for the latter from the results of the hourly observations registered at the 

 Surveyor General's Office, Calcutta, and computed in the Meteorological Office 



