1888.] occurred at Dacca on April 7th, 1888. 195 



Tlie observations contained in the above table, with those of a good 

 many other stations, are charted on a small map (PI. XXIV.) on which 

 are drawn the lines of equal pressure reduced to sea-level, which are 

 shewn by continuous lines, the lines of equal humidity in broken lines, 

 and those of equal temperature at 10 A. M. by dotted lines ; but in the 

 last case the temperatures are not reduced to their sea-level equivalents, 

 for the majority of stations which are shewn are in the plains of Bengal, 

 and do not therefore differ very much in height above sea-level, and, for 

 the purposes required in this paper, it does not appear that such a correc- 

 tion is necessary. The observations prove clearly that, so far as atmos- 

 pheric pressure was concerned, the changes were very small, and did not 

 denote that there was any particular disturbance going on in Bengal. 

 On the previous day, the 5th, the observations taken over the whole of 

 India for the India Weather Report had shewn that pressure was falling 

 over part of Orissa and tho neighbouring parts of the Central Provinces, 

 while over the whole of Bengal and Behar pressure was rising. On the 

 6fch April, or the day under review, pressure was falling decidedly over 

 Chutia Nagpur and parts of Orissa, while it was still rising over the 

 remainder of the Province, particularly in East and Worth Bengal. 

 Owing to these changes, a shallow area of comparatively low pressure 

 appears to have formed over parts of West Bengal and Chutia Nagpur, 

 though the lowest pressures in the province were actually recorded m 

 Behar and North Bengal. On this day also, the isothermal lines repre- 

 senting differences of 5° are very close to each other, particularly over 

 parts of North Bengal, shewing that there were great contrasts of tem- 

 perature over limited areas. The broken lines shewing equal degrees of 

 humidity are also very close over East and North Bengal, and, while 

 such stations as Berhampore, Kampore Bauleah, Bogi-a, Dinagepore 

 and the area to the west shew generally humidities below 20 per cent, 

 only 50 to 100 miles to the east of this area, humidities of about 70 per 

 cent, were generally reported. 



The distribution of the humidity and the wind directions over the 

 Province as laid down in the chart for the day (PL XXIV.) shew 

 most clearly that two very distinct wind currents were principally 

 affecting Bengal. There was an exceptionally dry westerly current 

 blowing from the centre of India over Behar, Chutia Nagpur, and 

 West Bengal, and even penetrating as far as North Bengal, for winds 

 were more or less westerly with very low humidity at Bogra, Dinage- 

 pore, and Rungpore. At the southern stations, a strong and very moist 

 southerly wind from the Bay of Bengal was blowing, givino-^ in com- 

 bination with the westerly winds from Central India, a south-westerly 

 breeze over considerable parts of the centre of the Province, while north- 



