1884.] Bains of Nortliern India. 7 



not known with sufficient precision to admit of its barometric register 

 being reduced to terms comparable with those of the Sind and Punjab 

 stations, I have compared the oscillations of the Quetta barometer with 

 those in the valley of the Indus, when barometric minima have appeared 

 in Upper Sind, and find that, with two very doubtful exceptions, in 

 January and February 1880, any fall of pressure at Quetta was either 

 simultaneous with the fall in Sind, or somewhat later. In one of these 

 exceptional instances, there was a slight fall at Quetta two days, and 

 in the other one day, before it took place at Jacobabad ; but on both 

 occasions, the great fall, when the minimum was established in Upper 

 Sind, was simultaneous at both stations. In such cases as that of the 

 25th January 1878 (when the minimum first appeared at Deesa) and 

 those of January, February, and March 1881 (when a barometric depres- 

 sion which had existed in Western llajputana throughout the cold 

 season, was simply intensified immediately prior to tne rainfall), there 

 could be no question of a depression travelling from the westward. 



But it is not only in North- Western India even, that barometric 

 minima are occasionally formed in the winter months : in the case of 

 the rain of the 10th to 13th January 1878, it first appeared on the 

 western half of the Deccan plateau ; in that of the 10th February 1879, 

 a long trough-shaped depression ran through the heart of India from 

 Belgaum to Lucknow, and, in that of the 15th to 18th February 1880, 

 it was first established in the Central Provinces, whence it was trans- 

 ferred to the Punjab ; and the distribution of pressure, in Northern 

 India, became strikingly similar to that which characterizes the rainy 

 season. 



There is, then, no reason to doubt that, notwithstanding that Nor- 

 thern India is in general and on an average an area of high pressure 

 in the Avinter season, relatively to lower latitudes, this condition is by 

 no means constant or lasting. The atmospheric pressure, in extra- 

 tropical India, more frequently than that of the peninsula, occasionally 

 falls below that prevailing over the seas to the south, causing vaj^our- 

 bearing currents to pour in from that direction; and these currents, in 

 ascending around the seat of minimum pressure, chiefly on the east and 

 north of the minimum, condense that vapour as rain (and on the hills 

 as snow^). This is a more or less regularly recurrent feature of the 

 winter season. 



Of the conditions which determine the formation of these barometric 

 minima, but little can be positively asserted in the present state of our 

 knowledge. That they do not originate in a local excess of temperature 

 in the lower atmospheric strata, is abundantly apparent ; the rise of 

 temperature that, in general, precedes the rainfall, and is accompanied 



