180 



H. P. Blanford — On the Climate of Bengal. 



[Nov. 



of Bengal. The former are deduced from 17 years, the latter from 1-1 years 

 observations. 



Mean Melative Humidity. 



Saturation 100. 



The quantity of vapour in the air of Calcutta, relatively to the dry air, 

 is then, on the average of the year, about twice as great as in that of London ;* 

 but the relative humidity of the former equals that of the latter only in 

 the three first months of the rains, which are among the driest months of 

 an European climate. 



The absolute humidity of the atmosphere is greatest on the coast of 

 Orissa and the Sunderban, and diminishes inland as the distance from the 

 sea increases. In the cold weather and spring months, this decrease is rapid 

 everywhere, except in Eastern Bengal. In Kachar, however, the quantity of 

 moisture in the air is as great as on the coast of Chatgaon, and even exceeds 

 it, excepting between the months of February and May. Daring the hot 

 weather months, the proportion of vapour to dry air increases steadily and 

 rapidly in all that part of Bengal in which the hot westerly winds are not 

 a regular phenomenon of the season ; that is to say, on the Gangetic delta, 

 in Eastern Bengal, and on the maritime plain of Orissa ; but on the high 

 ground further west and in Bihar, as well as generally in the N. W. Pro- 

 vinces, its increase is slower up to M^ay or June, and it then rises rapidly 



* In Calcutta the vapour of water constitutes on an average about two and a 

 half per cent, by volume of the atmosphere ; in London only one and a quarter. Next 

 to the temperature, this is perhaps the most important climatal difference of the two 

 places in all that affects health. 



