118 H. F. Blanford — Protracted Barometric Anomalies. [June, 



theless, though of protracted duration, these peculiar features are not 

 permanent. They characterise it may be a single season, or it may he 

 two or more seasons in succession, and then disajDpear. Second, that 

 these pecuHarities in the distribution of barometric pressure exercise an 

 important influence on the rainfall, by affecting the course and velocity of 

 the winds which bring the rain. The laws of this interdependence require 

 a prolonged study, but in certain cases in which the barometric anomaly has 

 been of unusual intensity, it has appeared that the rainfall of a season has 

 been deficient under the lee of a region in which the pressure has been 

 higher than usual relatively to the surrounding regions ; and that in the 

 lee of a region of relatively abnormal barometric depression, the rainfall 

 has been heavier than the average. This last relation, it was pointed out, 

 coincides with the law of rainfall in Cyclones ; the heaviest rain being in 

 advance of the storm vortex. 



The paper discusses the registers of pressure in Bengal, and the Bay, the 

 Central and N. W. Provinces, for the seven years 1868-1874, the data being 

 given in the form of Tables, shewing the total and relative barometric ano- 

 malies of a mxmber of stations. The first of these tables shew how much 

 the mean of the barometer readings of each month at each station ranged 

 above or below the average of the seven years, for the same month and sta- 

 tion. This difference is termed the total anomaly. In the second table, 

 the total anomalies of certain pairs of stations are compared month by 

 month, and it is found that as a general rule, the total anomaly of the 

 one instead of oscillating sometimes above and sometimes below that of the 

 other, remains higher or lower, as the case may be, for many months in 

 succession ; and sometimes through one or two years. This difference is 

 termed the relative anomaly. 



Some striking cases were described in which the relative anomaly has 

 been of unusual intensity ; more especially in 1868, when the North West 

 corner of the Bay of Bengal was the seat of a persistent barometric depres- 

 sion ; and in 1873, when there appeared to be an unusual depression in the 

 neighbourhood of the Nicobars and another in Oudh and the N. W. Pro- 

 vinces. 



A number of barometric charts were exhibited, most of which, however, 

 had reference only to Bengal and the neighboming Central and N. W. Pro- 

 vinces. Until last year it was impossible to obtain data from other 

 parts of India to compare therewith. The charts for the first eight months 

 of 1875, shew the distribution of pressure, wind direction and temj)era- 

 ture over the whole of India and the Bay of Bengal ; and it was pointed out 

 that in the course of a few years such a series would afford the best possi- 

 ble material for the further study of the problems now put forward. 



The paper will be published in full in the forthcoming number of the 

 Journal, Part II. 



