bs 
a... On the Whirling Action of the 
with the rotative and progressive 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 direc- 
tions 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 moved from their position, or swept onward 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 pros- 
trations for the most part take place either at the outset or under 
the middle portions of the whirlwind; while on the left or re- 
verse side, up to the line of the apparent axis, and even across 
the latter, they occur chiefly under the closing action of the whirl, 
as above described. The violent effects of this central and clos- 
ing action are more clearly seen as we advance from the left-hand 
margin towards the centre or apparent axis of the path. 
F'rom the causes to which I have just alluded, 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 vi0- 
lence is found to coincide nearly with the line which separates 
the inwardly inclined prostrations of the two Opposite sides of the 
track.* e latter line or apparent axis of the track is some- 
times called the line of convergence, and is indicated on the fig- 
ure by the line and arrow ec. Along this line, from the causes 
just mentioned, aided also by the elevating forces about the axis, 
many of the trees are swept onward, 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 trees are not unfrequently torn out of the ground and 
carried onward to considerable distances. 
It is proper to state here, that in the tracks of all the tornadoes 
which I have had opportunity to examine, and in some, at least, 
* The line of greatest violence, for the most part, is found somewhat to the right 
of the line of convergence. 
spe * ; 
& 
