226 



server, over whom the centre should pass, after exposure to the 

 greatest violence of the whirl on one side, could be suddenly exposed 

 to an equally violent but contrary wind on the opposite side. 



The discordancy of the whirlwind theory (agreeably to which a 

 storm, travelling towards the north-west and whirling to the left, 

 must have its greatest velocity in a south-easter on the north-eastern 

 limb, where the tangential velocity coincides with the progressive mo- 

 tion), with the fact stated by Edwards, and admitted by Redfield, that 

 on the limb alluded to, in the storms alleged so to move, there is the 

 least violence. 



The obvious consequence, that if our north-eastern gales be due to 

 a whirlwind, moving along the coast of the United States at the rate 

 of twenty -seven miles nearly per hour, whirling to the left, the gyra- 

 tory velocity on the south-eastern limb must be more than fifty miles 

 per hour greater than on the north-western limb ; so that a much 

 more violent gale from the south-west, at sea, must be simultaneous 

 with the prevalence of every north-eastern gale along the coast ; all 

 of which is contrary to experience. 



The palpable inconsistency of representing tornadoes as generated 

 by the conflict of winds, arising from the earth's motion, with islands, 

 and yet as ensuing in a calm, where there are no active currents to 

 meet each other.* 



To this list of errors, the following, since detected, might be sub- 

 joined : — 



In opposition to the " long cherished theory of calorific rarefac- 

 tion,'''' entertained by the modern meteorological school, Mr. Redfield 

 ascribes all winds to a rotative movement, arising from rotary or 

 orbitual motion of the earth, and conflicts between trade winds and 

 islands, and yet denies that he has advanced any theory of storms 

 upon assumed scientific principles. 



He repeats that the general winds would be more uniform, brisk, 



* If tornadoes originate in calms, where there are " no currents to meet each 

 other" and if they be attended by vertical currents about the axis, this must 

 of necessity be productive of centripetal currents, which will probably gyrate 

 from their obliquity. But what other cause can be productive of the upward 

 current under such circumstances, if it be not an inferior pressure over a cen- 

 tral space? 



Redfield's account of whirlwinds excited by fire demonstrates, that a cause 

 producing an upward current in the atmosphere, may, under favourable^ cir- 

 cumstances, be productive of tornadoes and concomitant electrical discharges. 

 See Silliman's Journal, for 1839, Vol. XXXVI. page 50. 



