532 Note on the Sail-storm of Thursday the 24th March. [No. 5 



The thunder and- lightning .continued vividly for half an hour or 

 more after the cessation of the fall, hut gradually the clouds dissolved 

 and by 9 o'clock the sky was clear. The wind continued from the 

 gouth-east for the remainder of the evening. 



The fall was very local. At Serampore there was rain hut no hail 

 (Friend of India) ; at Dum Bum there was no fall simultaneous with 

 that of Calcutta, hut a heavy fall occurred about half or three quarters 

 of an hour later, which Mr. Boulnois who left Calcutta after the end of 

 the hail-storm, experienced on the road to Bum Dum (but which 

 did not reach Calcutta). At Koolnah, according to the newspapers, 

 there was also a heavy fall, and a stone is said to have fallen there of 5 

 seers (10 lbs.) in weight. This, however, wants confirmation. The total 

 fall at Calcutta, as estimated by the lower Rain guage at the Surveyor 

 General's Observatory, was 1.22 inches. 



It would be a point of some interest to ascertain the direction of the 

 wind, temperature and other meteorological data in the northern parts 

 of Bengal e. ej. at Moorshedabad, Purneah, Malda, Kissengunj, &c, 

 in order to determine the causes of this interesting hail-fall. Hail, as 

 is remarked by Sir J. Herschel, seems always to depend on the sudden 

 introduction of an extremely cold current of air into the bosom of a 

 quiescent,* nearly saturated mass. Now the dew point at 5 o'clock as 

 calculated by Apjohu's formula from the observed temperatures of the 

 wet and dry bulbs was 84,° the dry bulb thermometer being 86.6. The 

 air was therefore very near saturation, as might be expected of a 

 heated wind, which had recently swept over many hundred miles of a 

 tropical sea. Were such a wind met by a cold current from the Hima- 

 laya, we should have the conditions required to produce hail, but in this 

 case we should expect to find some indications of the northerly current 

 in the direction of the wind, and in a lower temperature at some of the 

 northern stations. It is not necessary that the temperature of this 

 current should be below the freezing point. Its collision with the 



above paper it was observed by the Honorable Mr. Beadon, and confirmed by 

 other observers, that many of the later stones were very irregular and 'perfectly 

 transparent lumps of ice. One in particular was described as resembling a 

 double fanged tooth in form. These appeared to be agglomerated stones. 



# The air could scarcely be said to be quiescent in this case as previous to 

 the storm and again after its close the south-east wind blew strongly, but this 

 would be checked when met by a strong northerly current, and an ascending 

 current produced. 



