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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 
