130 Irregularities of Atmospheric pressure in Bengal , Sfc. [No. 2, 



The distribution of atmospheric pressure shown by this table is 

 very different from that shewn by the table for 1868. The Saugor 

 Island means are throughout equal to or higher than those of Cal- 

 cutta, and those of False Point equal to or higher than those of 

 Cuttack. Of the area of depression in the head of the Bay, which 

 was so marked and constant during the monsoon of 1868, not a 

 trace reappears. This season the seat of minimum pressure is 

 transferred to Hazaribaugh and Monghyr,* and here it was persistent 

 nearly to the close of the monsoon, deflecting the winds and apparent- 

 ly determining the distribution of the rainfall, just as the Saugor 

 Island depression of the previous year had done in the lower part 

 of the delta. 



This depression first became marked in April, in which month 

 the lowest mean readings are those of Hazaribaugh and Patna, 

 Monghyr being wanting. In May the difference was greater and in 

 June these three stations alone lay within the isobaric of 29'5. In 

 June and July the pressure was about the same at Hazaribaugh 

 and Monghyr, but in August and September it rose at the former 

 more rapidly than at the latter station, and the barometric mini- 

 mum lay above Monghyr. f Throughout the three first months of 

 the rains, and indeed nearly to the end of September, the vapour 

 bearing monsoon was then arrested in its normal course towards 

 the N. W. Provinces by a persistent atmospheric depression in the 

 region of the Curruckpore hills and Hazaribaugh, and it was not 



* In the abstract of the paper given in Proc. As. Soc. for January 1870, it was 

 stated (p. 93) that in March, a slight depression appeared over a region inclu- 

 ding Berhampore, Monghyr, &c, that in May it was intensified especially over 

 the first named station and reached its lowest point in June, and that there 

 was a mean difference of 014 of an inch between Calcutta and Berhampore. 

 On re-examining the registers and laying down their barometric means of the 

 stations for each day in curves, an instrumental error has been detected in the 

 Berhampore register which affected it from the 15th April to the 15th July, 

 and which caused the mean pressure to be recorded as rather more than 0*1 

 too low. A corresponding correction has been applied to the register in the 

 above table, but since the correction can be determined only for the beginning 

 and end of the period, and is assumed to be the same throughout, the results are 

 marked with a [?]. It results from this that the depression did not move 

 westward as originally stated, but changed as now stated in the text ; and that 

 the cyclone of June did not move dix-ect to the place of minimum pressure, 

 though (as I am still of opinion) its course was probably affected by the exist- 

 ence of the local depression. 



t Except Roorki which in this month was lower than any of the Bengal 

 stations, but the barometer has not been compared and there is much reason for 

 the belief that it reads low. 



