22 On the prevailing Storms of the Atlantic Coast. 
winds, which, owing to partial obstructions or other causes, frequent- 
ly form into eddies or whirls, the rotative motion of which increases 
with their progress as they are wafted along by the surrounding at- 
mospheric current, raising clouds of dust and other light substances, 
till they finally become broken or dissipated. ‘The writer has seen 
a whirlwind of this kind, operate with so much violence in passing 
over a river, as to raise a white cloud of spray to the height of some 
forty or fifty feet, which disappeared before reaching the opposite 
shore. Whirlwinds of a still severer character sometimes occur, and 
are, by seamen, denominated white squalls, from the white appear- 
ance of the spray thus raised into the atmosphere. Doctor Frank- 
lin, it is well known, maintained the identity of these smaller whirl- 
winds with water spouts. 
Another class of whirlwinds, of more formidable character, are 
those which sometimes attend the thunder storms, or gusts, of the 
Atlantic states, and more frequently, ravage the fields and forests of 
e regions west of the Alleghany mountains, carrying desolation and 
death in their progress. Like the smaller class, they are carried 
along by the attendant wind of whose mass they form an integral 
portion. Their ravages are generally confined to a narrow track, “oft 
ten of but few yards in breadth. Rising at times, over objects in 
their path, and leaving them untouched, they again descend to the 
surface, and continue the work of destruction. The chief force of 
these winds evidently consists in the almost inconceivable rapidity 
with which the mass revolves about its own axis of rotation, a veloci- 
ty which is, therefore, unopposed, except by the obstacles brushed 
upon at the earth’s surface, and which is maintained in full activity 
by the concentric, or tangentical pressure, or action of the surround- 
ing portions of the atmosphere. 
It is believed that no valid reason can be shown, why much larger 
masses of the atmosphere may not acquire, and develope, rotative 
movements, similar to those which are exhibited by whirlwinds, and 
the demonstrated existence of the latter ought to free us from the 
charge of maintaining a mere hypothesis, when we ascribe the same 
character to such storms as that which we have already described, 
if we can show that they are attended with corresponding phenom- 
ena. 
It is demonstrably evident, that at any point over which the center 
_ of a whirlwind may pass, the wind must, at the moment in whie 
this center passes, suddenly change to a direction almost exactly op- 
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