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twenty miles long, and that it passed over its own length in 

 an hour ; or, in other words, that it only moved at the rate of 

 twenty miles an hour, carrying the whirlwind along with it ; 

 for that the whirlwind was caused by the cloud, and had no 

 connexion with the tranquil current of air which bore it, was 

 evident. 



" Where this immense cloud was formed, and charged with 

 materials for such prodigious torrents of rain, and by what 

 means that immense weight was supported, are problems for 

 the meteorologist. Supposing that the rain fell as heavily 

 in other places as in Birmingham — and every account makes 

 the supposition probable — every square superficial foot of the 

 under surface of the cloud must have given out two inches of 

 water per hour; and calculating six gallons to the cubic foot, 

 every superficial square foot must have deposited one gallon 

 per hour during its course ; and if that course only lasted six 

 hours, each superficial foot must have given out 50lbs. of 

 water in that time. 



" Whether the cloud actually carried this weight of 501b. on 

 each square foot, and if it did, what was the sustaining power 

 which enabled it to do so, would not be easily told; but another 

 question suggests itself, was all, or the greater part of the 

 water deposited during its course, generated from time to time in 

 the cloud ? One thing seems clear, constant lightning accom- 

 panied the release of the water from its aerial carriage, and a 

 whirlwind seems to have been necessary to supply the con- 

 sumption of atmospheric air. 



" The great accumulation of heat for two or three days 

 before such violent thunder-storms, seems to indicate that 

 they are preceded by a cessation of some ordinary heat-absorb- 

 ing atmospheric processes over the places where the storm 

 afterwards passes. In the case of this storm Mr. Onion says, 

 that the barometer had been in a very unsettled state for some 

 days previously, often in the course of twenty-four hours rising 

 or falling to a considerable amount, although not followed by 



