of the Providence Tornado. 49 
It will readily be seen that this eccentricity of the axis, on 
the visible track, will be in proportion to the progressive velo- 
city of the tornado; other things being equal. ‘Thus, if Mr. 
Allen be nearly right in his estimate of the rate of progress in 
the Providence tornado, the eccentricity of the axis of its path 
will be generally less than is shown in figures 4and 5. On 
the other hand, if the progressive velocity should be as great 
as Professor Loomis informs me he ascribes to the tornado of 
February last, in Ohio, viz. about forty miles an hour, the ec- 
centricity would in such a case be greatly increased, showing 
the axis as far outward, perhaps, as would be in line with m, 
or f/, in these two figures. 
From this examination it appears to result, that an observer 
who follows the track of a tornado after its departure, wil] find 
on one side of the apparent axis of its path, 7f 2¢ be a whirlwind, 
a continued series of prostrations pointing almost invariably 
onward and inward, with various degrees of inclination to the 
course of the path; while on the other side of the axis a 
narrower band or belt of prostrations will be found, which are 
also inclined mainly inward and onward, but showing greater 
inclinations from the line of progress, together with frequent 
cases which incline more or less backward and sometimes even 
outward from the course of the tornado. 
It may also appear, that a want of proper attention to the 
necessary conditions of the prostrating power in a progressive 
whirlwind, can alone induce us to ascribe such effects to sup- 
posed antagonistic winds, blowing simultaneously in opposing 
directions. 
Leaving, for a moment, the more tangible features of this 
inquiry, we may now take some notice of the more outward 
portions of the “cone” or whirlwind, which are supposed not 
to be comprised in figure 4. Assuming here the involuted 
and inward motion, with its upward discharge at the centre, 
it follows that the impulsive accession of air which is necessary 
for maintaining a violent whirlwind action, must come in ho- 
rizontally, and in the same gradually involuted courses; or 
must descend in like manner from a higher region, in and 
around the outward parts of the whirling cone. I have long 
since been led to believe that this impulsive accession comes 
from both these sources, but chiefly from the latter ; and that 
this motion of accession and support is spirally downward in 
the outward portions of the whirl; the latter being, in its 
higher portions, often greatly expanded, as noticed by Mr. 
Allen. 
The evidence on which this opinion rests, can be but par- 
tially alluded to here; but I will suggest the following con- 
Phil. Mag. 8. 3. Vol. 22. No. 142. Jan. 18453. EK 
