1870.] Irregularities of Atmospheric pressure in Bengal, 8fc. 125 



liarity, affected not one only, but two or three neighbouring stations 

 in different degrees, and lasted for some months. 



It was not, however, until another S. "W. monsoon had afforded 

 me the means of comparing the barometric features of the same 

 season in two consecutive years, that I could be justified in assuming 

 any correlation between these local peculiarities of atmospheric 

 pressure, and the variations in the rainfall. There has hitherto 

 been very little systematic observation of the barometer in India, 

 that is susceptible of comparative treatment, and very much 

 remains to be done to ascertain the normal distribution of atmos- 

 pheric pressure during our monsoons. To determine whether any 

 local peculiarity is normal or abnormal, at least two registers for 

 corresponding seasons must be compared. This has now been 

 done for the SW monsoon, and I am justified in concluding, that 

 the local depressions which I shall now describe, and which appear 

 to me to be intimately related to those variations of the rainfall 

 which I have already noticed, are peculiar to the year and not 

 recurrent. 



I take first of all the SW monsoon season (May to September) 

 of 1868. The following table (extracted from my official report) 

 gives the mean barometric pressure* of each of the monsoon 

 months, at all the stations from which I have reports for the period 

 in question. They are reduced to 32° Fahr. and mean sea level. 

 May. June. July. Aug. Sept. 



Port Blair, ? 29-810* 29-835* 29-819*29-853* 



Madras, 29,800 '742* '756* -772 .792* 



Akyab, -850 -753 -756 -720 -797 



False Point, -736 -567 -562 -575 -654 



Cuttack, '754 -613 -615 -568 *735 



Chittagong, -802 -626 -657 -630 -740 



Saugor Island, .... '736 -522 '535 -475 -616 



Calcutta, '781 -570 603 -601 699 



Hazaribaugh, .... '720* -546* -509* ? ? 



* The means are obtained from the observations recorded four times daily 

 viz. 4 a. m., 10 a. m., 4 p. m., and 10 p. m. on every day in the monch, 

 except those marked with an (*) which are the means of the 10 a. m. and 4 

 P. m. observations only. I have shewn, in the Report, that the means thus 

 obtained are comparable to within '01 of an inch. 



17 



