10 C. Little — The recent excessive heat in Bengal, [No. 1 



latter half of April and May; that under normal conditions it moves 

 westward in advance, and renders possible the commencement of mon- 

 soon weather in Bengal. Any direct information regarding such at- 

 mospheric conditions is not readily attainable, as what meteorological 

 observers collect refers to the ground level only. But I occasionally see 

 in the local papers items of information of the greatest possible interest. 

 I will give one of these from memory which I saw last year in a copy of 

 the JEnglishman about the end of April or beginning of May. 



It may be in the recollection of some that in the latter half of 

 April 1902 unusual weather was experienced in East Bengal and the 

 adjacent part of Assam. Its chief feature was heavy rain ; 10 to 20 in- 

 ches fell over a wide area in as many days, and if the quantity of rain- 

 fall were taken as a definition of monsoon weather I should say that 

 last year in those eastern districts there was a stronger south-west mon- 

 soon during the latter half of April than at any other time up to the 

 end of October. A correspondent of the Englishman writing from one 

 of these eastern districts told of the heavy rainfall and went on to give 

 the information which interested me. He described how they had been 

 bombarded by thunderstorms, and how the storms had come up from 

 every point of the compass. Now seeing that thunderstorms drift with 

 the upper atmospheric current, the variable directions of these thunder- 

 storms showed that there was in that area of heavy rainfall in East 

 Bengal the stagnant condition of the upper air. I believe that if such 

 information were available we would find that year after year there is 

 the same stagnant condition, and that it is only noticed in extraordinary 

 circumstances such as prevailed in East Bengal last year. 



I will anticipate the explanation of the heat in Bengal this year to 

 some extent to show how the rainfall last year was possible with the 

 still condition of the air indicated by the thunderstorms referred to 

 above. The overhead air last year was cold whereas this year it has 

 been warm. The difference is the same as for a condensing engine work- 

 ing with the cold water of northern seas and the hot water of tropical 

 seas : that is, the vapour with which the air in Bengal is at all times 

 well supplied was much more easily condensed last year than this, and 

 with that condensation there was a much more effective overturning of 

 the layers of atmosphere due possibly to the electrical developments. 



I will quote the same high meteorological authority as before, re- 

 garding the condition of the air favourable for the development of thun- 

 derstorms : — 



" A strong and even abnormal vertical temperature gradient accom- 

 panies the formation of thunderstorms, which are attended by an inver- 

 sion of the over-lying strata," 



