26 C. Little — On two remarkable rain-bursts in Bengal. [No. 2, 



passed over Bengal, one of the most noticeable on the meteorological 

 record of the time is the heavy rainfall in Bengal Proper, between 

 8 a.m. on the 29th, and 8 am. on the 30th June. It appears in the 

 record as rainfall of the 30th June. 



I may, perhaps, be allowed to digress here for a moment to point 

 out the difficulty, which I shall refer to later on, in establishing the 

 sequence of events in atmospheric matters. The only record of such 

 events is what the observers note at certain fixed hours — mostly 8 A.M., 

 supplemented at a few places by observations at 4 p.m. If any change 

 passes so rapidly over the land that it is completed within the 24 hours, 

 between 8 a.m. of one day, and 8 a.m. of the next, it appears, as a simul- 

 taneous change and at times, an important part of the change is lost 

 altogether. For instance, when a cyclone of small extent passes over 

 an observatory the rapid fall of pressure during the approach of the central 

 area and the rapid rise, after its passage, may occur in a few hours, and 

 neither will be shown by the 8 A m. record of that station, unless the 

 passage occurs about that hour. For that reason, the pressure record of 

 a disturbance, with a high rate of progress, is of less value in a historical 

 survey than are those for temperature and rainfall. It would be a very 

 awkward circumstance if the rain which falls, say in the afternoon, were 

 to evaporate before it could be measured next morning. But the rain- 

 fall remains and though some rise of temperature occurs after the 

 passage of a disturbance the recovery is slower than that of pressure, 

 more especially if there should be a good deal of cloud at the time. 

 Because of this difficulty as regards the record of pressure changes 

 I rely more on the rainfall and temperature changes to prove the 

 progressive motion from north to south for the disturbance which 

 accompanied and no doubt caused the rainfall of the 30th June. 



The second disturbance with which the rain-burst of the 11th 

 August was associated was no less remarkable than the first, but it was 

 less striking to the ordinary observer because there was not the same 

 reversal of temperature. In one respect it was even more noticeable 

 and that was as regards the pressure changes which in this case, 

 strongly support the view that the disturbance entered India from 

 Thibet. A reference to the Indian Daily Weather Report, will show 

 that the fall of pressure preceding the June rainfall, occurred almost 

 simultaneously over the whole of India so that pressure changes alone 

 would not be sufficient to prove that the disturbance did not come from 

 some other direction, from the Bay of Bengal for example, but the 

 pressure changes preceding the August rainfall leave no room for doubt 

 that that disturbance did not originate over the Bay. The fall of 

 pressure began in the north-eastern Himalaj'as and from there, extended 



