26 Mr. W. C. Redfield on the Tornado •whiek visited 



greater portion of the prostrations on the reverse side of the 

 axis should be found in a backward direction : and so they 

 would undoubtedly be found, were it not for the inward and 

 the progressive action. But the force is here so far lessened by 

 the reverse action above noticed, that in most cases only a small 

 portion of the trees exposed will be thus prostrated : while 

 the crreatest force of the whirlwind, on this side, is felt near 

 its last or closing portion and towards the apparent axis, 

 where the inward, together with the rotative and progress- 

 ive forces, seem to combine their influence in the closing 

 rush towards the heart of the receding vortex. This appears 

 to account for the nearly opposite directions of prostration 

 found on this side, and it is apparently by this more violent 

 closing action, that many trees which were first overthrown 

 in a direction nearly across the centre of the path, were 

 again overturned inversely, and often carried forward nearly 

 in the course of the tornado. It is proper to remark here, 

 that an attentive examination of these effects has served to 

 convince me that on the right and more central portions of 

 the track the prostrations for the most part take place either 

 at the outset or under the middle portions of the whirlwind, 

 while on the left or reverse side, up to the line of the apparent 

 axis, and sometimes across the latter, they occur chiefly under 

 the closing action of the whirl, as above described. The vio- 

 lent effects of the latter are more clearly seen as we advance 

 from the left-hand margin towards the centre or apparent 

 axis of the path. 



From the causes to which I have just alluded, aided by the 

 elevating forces about the axis of the tornado, the effects are 

 usually more violent on and near the line passed over by the 

 axis, than in other portions of the track. This line of greatest 

 violence is found to coincide nearly with the line which se- 

 parates the inwardly inclined prostrations of the two opposite 

 sides of the track*. The latter line or apparent axis of the 

 track is sometimes called the line of convergence, and is in- 

 dicated on the figure by the line and arrow cc. Along this 

 line, from the causes just mentioned, aided also by the ele- 

 vating forces about the axis, many of the trees are carried 

 forward and left with their tops in a direction nearly parallel 

 to the course of the tornado ; forming an apparent, but not 

 a just exception, to the more lateral direction which pertains 

 to most of the trees prostrated by the onset of the whirlwind, 

 near the central portions of the track. Indeed, the central or 

 closing violence of the advancing whirl is here so great, that 



• The line of greatest violence, for the most part, is found somewhat 

 to the right of the line of convergence. 



