10 ACCOUNT OF A TOENADO, 



Let A B, Fig. II, represent the track of a tornado, the dotted line C D tlie iieiglit 

 or weight of the atmosphere at New Harmony, at 3 P. M., and at 6 P. M., one 



Fig. II. 



being one hour and a half previous, the other one hour and a half subsequent, to the 

 passage of the tornado. Imagine E G to represent Espy's ascending column of air, 

 with horizontal conflux at the base from the surrounding space ; suppose the column 

 to reach the toj) of the atmosphere, G D, and the air in the ascending column to be 

 spreading out and overlapping the air in the surrounding regions, in the vicinity of 

 the tornado, and by increasing the weight of the air around, causing the barometer 

 to rise. Suppose E to be the meridian of New Harmony, over which the column, 

 or tornado, is passing. Suppose jPto be the meridian of Leavenworth, and that F 

 is ninety miles distant from E, and now imagine the column in motion, and pro- 

 gressing towards F at the rate of a mile per Biinute ; and that after an interval of 

 one and a half hours, it has reached F. During this progress of the column we 

 may conceive the translation of an atmospheric wave, and as the meteor passes on 

 towards Leavenworth, we may imagine the gradual flowing away of the air, and 

 the restoration of the equilibrium of the atmosphere to the degree that existed 

 previous to the coming up of the meteor, or disturbing cause. 



In conclusion, in referring to the different causes from which it is said tornadoes 

 originate, my opinion is that the phenomena are incompatible with the rotatory 

 hypothesis ; and this opinion is strengthened by my inability to conceive, how any 

 deflection of trade-winds by mountains, or action on the air by the different rota- 

 tive velocity of the earth's surface, can originate these meteors : I cannot conceive 

 the probability of the bodily rising, on a particular point of the intertropical plain 

 of America, of an intensely heated column of air, with an ascensional force suffi- 

 cient to carry it into the upper strata of the atmosphere, vv'itli the full v/esterly 

 energy derived from the earth's rotative velocity ; producing in its course a ripple, 

 whichj on its return, strikes far below into the lower current, creating the necessary 

 condition of a rotatory storm, in which a mass of air, animated with immense velo- 

 city, forces its way through an atmosphere, either at rest, or moving in an opposite 

 direction, creating vortices, subsisting and vv^andering over great tracks, long after 

 the original impulse is withdrawn ; I cannot conceive, whatever may be the velo- 

 city originally communicated to any body of air, how at 800 miles distance from 

 the tropic, it could still have the power to subsist, and, without further support, 

 have energy sufiicient to continue its destructive career for 250 miles, tearing down 

 trees at the rate of 7,000 orf a mile, per minute. 



