200 



Pedler and Crombie — On the Tornado which 



[No. 2, 



passed and to the south-east of which the tornado was formed, there were 

 from the 6th to the 8th the most striking and excessive changes in 

 humidity. 





Average 



HUMIDITY- 



-Saturation = 100. 



District. 













April 6th. 



April 7th. 



April 8th. 



April 9th. 



A. — Stations in Behar, Chutia Nag- 











pur, and North Bengal acted on 











by dry wind current 



16 



40 



18 



14 



B.— Stations in South and South East 











Bengal ... 



64 



67 



54 



39 



C. — Average of Stations, Berhampur, 











Rampur Beaulah, an^ Bogra 











representing an area in a N. E. 











direction over which apparent- 











ly the barometric minimum 











passed and to the south east 











of which the tornado was 











formed 



21 



62 



24 



16 



Difference between B. & 0. 



43 



6 



30 



23 



These rapid changes of humidity necessitate equally rapid changes 

 in the air currents affecting the areas, and it is therefore clear that, in 

 Central and North Bengal, or to the north north-west and west of the 

 position in which the tornado was formed, or at all events in which it 

 made itself felt during the period 6th to 8th April, 



1. There were rapid changes in the areas affected by two wind 

 currents of almost opposite nature. 



2. There were great contrasts of temperature and humidity at 

 neighbouring stations over the same area. 



3. There is evidence to shew that there was a shallow area of 

 comparatively low pressure, or a barometric minimum, which passed in 

 a north easterly direction through the centre of the Province frqin. the 

 6th to the 8th April, or at the time of the formation of the Dacca storm, 

 In other words, the Dacca tornado was formed to the south-east of the 

 track of a feeble low pressure area, and to the south-east of great con- 

 trasts of humidity and temperature, as is always found to be the case ii^ 

 America by Mr. Finley and others. But, as before stated, these can only 

 be predisposing causes, and what the immediate cause of the formation 

 pf the storm may have been it is impossible to say ; and, though it is con- 

 ceivable that the violent fluctuations of the opposing air currents above 

 referred to may be in some distant way connected with its causation, or 

 with rendering the formatiqn of such a storm extremely probable, yet it 

 js clear we are far from having arrived at its actual cause, 



