82 Notices of Tornadoes^ 6fc. 



III. — On Tornadoes, and (Er sled's Memoirs respecting them. 



To the Editors of the National Gazette. 



Dear Sirs, — I believe it is generally admitted by electricians 

 that the enormous discharges of the electric fluid, which, during 

 thunder gusts, take place in the form of lightning, are the conse- 

 quence of the opposite electrical states of an immense stratum of 

 the atmosphere coated by the thunder clouds, and a corresponding 

 portion of the terrestrial surface. In a memoir published in the 

 5th volume of the American Philosophical Transactions, repub- 

 lished in Silliman's Journal, vol. 32, for 1837, I had endeavored 

 to show that the tornado was the consequence of the same causes 

 producing in lieu of lightning, an electrical discharge by a verti- 

 cal blast of air, and the upward motion of electrified bodies. ^ In 

 your Gazette of the 30th ult., you have republished an article by 

 the celebrated QErsted, in which it is alledged that tornadoes or 

 water-spouts cannot be caused by electricity, because there is no 

 evidence proving that persons exposed to them have experienced 

 electrical shocks. To me it appears evident that the scientific 

 author confounds the different processes of discharge to which I 

 have alluded, the one occurring in thunder gusts, the other in 

 tornadoes ; also that he has forgotten that a shock can be given 

 neither by a blast of electrified air, nor by a continuous electrical 

 current, a transient interruption of the circuit being indispensable 

 to the production of the slightest sensation of that nature. If a 

 person, having a conducting communication between one of his 

 hands and a charged surface of a well insulated battery, hold in 

 the other hand a pointed wire, the battery will be discharged 

 through him and through the wire, producing a blast of electri- 

 fied air from the point, without his experiencing any shock ; nei- 

 ther would a shock be given to any person by exposure to the 

 blast thus produced. 



This form of electrical discharge to which I ascribe tornadoes, 

 in which electricity is conveyed from one surface to another by 

 the motion of air or other movable bodies intervening, is by ¥a.v- 

 aday designated as " cow^;ed^ow," from the Latin "conveho," to 

 carry along with. 



In the comparatively minute experiments of electricians, the 

 process of convective discharge, is exemplified not only by the 

 electrified aerial blast, but likewise by the play of pith balls, the 



