1S76,] Barometric Anomalies. 35 



part of the atmosphere is subject, certain states 

 tend to perpetuate or reproduce themselves in 

 the same region, in such manner as to maintain 

 a constant difference in the mean or average pres- 

 sures of two neighbouring regions; and that this 

 tendency to a constant local difference is in cer- 

 tain cases maintained throughout those great re- 

 volutions of atmospheric density, composition, 

 and movement which accompany the alternations 

 of the monsoons. Nevertheless these states though protracted are 

 not permanent, and disappear after a longer or shorter time. Sometimes 

 suddenly, but more frequently by a graduated decrease. 



When this class of phenomena first attracted my attention, my first idea 

 was, as would probably occur to most, that the instruments used for measur- 

 ing the pressure had either become defective, or had been displaced from 

 the vertical position or moved to a different elevation, without the fact having 

 been reported. I accordingly had the instruments recompared and ascertained 

 by careful enquiry whether any removal had taken place, but failed to ob- 

 tain any explanation of the observed anomalies. Longer experience has 

 shewn that two or more neighbouring stations, occasionally participate in 

 the same condition of protracted excessive or deficient pressure ; and where 

 stations exist intermediate in position between those at which extreme 

 opposite conditions prevail, the former continue to shew an intermediate 

 condition. I should add that, as far as regards Bengal, I have given the 

 utmost care to ensure that all barometric observations shall be rigorously 

 comparable, and after a careful consideration of all the circumstances, I am 

 able to see no reason to doubt the validity of the phenomena indicated by 

 the registers.* 



* The most remarkable case of protracted differences of pressure, which are never- 

 theless not permanent, is that shewn by False Point and Cuttack, as compared with 

 the surrounding stations. The registers shew that after remaining abnormally low 

 throughout the year 1868, the pressure rose at the beginning of 1869 and at False 

 Point remained unusually high throughout the years 1869, 1870, and 1871. At the 

 beginning of 1872 it again fell, and remained relatively low during the two years 

 following. Now at False Point the same instrument (a marine barometer of the 

 Fitzroy pattern) was used continuously by the same observer, and, I am assured, 

 in the same place, from the time when the station was originally established up 

 to the end of 1872; it was then replaced by a marine barometer on the Kew - 

 principle, without any change in the general value of the readings. At Cuttack 

 the original instrument was replaced towards the end of 1869, but the two were 

 read simultaneously for a fortnight, and, after applying the corrections which had been 

 previously determined in Calcutta, the readings were foimd to be identical. The second 

 instrument was again replaced in December 1872 by a Casella's standard, which was 



