40 John Eliot — On the occasional Inversion of the Temperature [No. 1, 



The following hence gives the chief features of the anti-cyclonic 

 weather immediately following a cold weather storm during which heavy 

 general snow has fallen in the Afghan highlands and the Himalayas : — 



(a.) — Pressure is excessive in Upper India and unusually clear bright 

 fine weather prevails. Strong westerly winds set in over 

 Upper India and extend rapidly eastwards. In Bengal 

 these winds displace the light southerly or easterly winds 

 which prevailed during the previous disturbed weather. 



(b ) — During the stormy weather both day and night temperatui'es 

 are very low at the hill stations, but, with the melting of the 

 snow, temperature rapidly increases and the ordinary anti- 

 cyclonic conditions of increased temperature are again exhi- 

 bited at these stations. The important factor in determining 

 this change of temperature conditions appears to be the melt- 

 ing of the snow from all the lower elevations. 



(c.) — During the disturbed weather the day temperature in Upper 

 India is below the normal and the night temperature is 

 above it. In Bengal and Behar, in consequence of the pre- 

 valence of light southerly and easterly winds, both day and 

 night temperatures are considerably above the normal and the 

 weather sultry and oppressive. The disappearance of the 

 disturbance is usually followed by a rapid reduction of both 

 the day and night temperatures. This accompanies a complete 

 shift of wind from some southerly to some northerly direction 

 and the prevalence of unusually clear bright skies in which 

 the solar radiation is even greater than usual. This passage 

 of a wave of cold is hence evidently due to the intrusion of a 

 body of cold air advancing from Upper India or the Hima- 

 layan mountain region into the Gangetic plain and Bengal. 



{d.) — The setting in of these winds produces a very rapid reduc- 

 tion in the humidity of the air and the amount of vapour. 

 The reduction is far greater in Bengal than in the interior, 

 and is sometimes excessive. 



(e.) — In consequence of these large changes of humidity and tem- 

 perature, the periods immediately following cold weather 

 storms in Upper India are especially cool, pleasant, and brac- 

 ing in Bengal and stand in marked contrast to the weather 

 prevailing before and during the existence of the storrns. 



We proceed to give an explanation of these facts. 



The chief feature of the cold weather in Upper India is great still- 

 ness of the air, the stillness being most marked at night. 



The following table gives the amount of winds measured by the 



