ra ——— 
! 
| 
H. &. Whitfield on Tornadoes in the Southern States. 99 
to the surface. It precisely resembles a column of black smoke, 
such as pours from the pipes of a steamer burning pine wood ; 
it isin fact condensed vapor or cloud, intensified in blackness 
by the dust and rubbish carried up from the ground. The 
tornado is a shell or hollow cylinder of air, and all its energy 
lies in its rotating rim which is powerfully ee by two 
antagonistic forces, centrifugal and centripetal. The rapid 
whirl draws the air from the center toward the circumference 
where it is met and opposed by the in-rushing winds. re 
is, consequently, a rarefaction, a great reduction of temperature 
by expansion, and condensation of vapor within the shell. 
e spout does not hug the earth continuously, but rebounds 
or ricochets along the uneven surface, often skipping the valleys 
but generally desolating the hills. It is disposed, however, at 
every recurrence to strike at the same points. It is not an 
established fact, but it is commonly believed, and with some rea- 
son, that the tornado does, in the course of years, return along its 
beaten path, and that it is unsafe to build where one has ever 
passed. The house in Pickens county stood on a hill from 
. Which a log cabin had been blown away some thirty years be- 
ore. I witnessed the last of three, which have passed along 
the same track. Near Hernando, Miss., three have followed an 
unvarying line. It is probable that there are some localities 
more favorable than others to the generation of these storms, 
and if this is true, then the law of direction, hereafter explained, 
accounts for their progress along the indicated path. _ 
uch an opportunity, as fell to my lot, of witnessing the 
formation and course of a tornado is rarely enjoyed, and the 
phenomena observed on that occasion are of great value in 
illustrating the origin of these whirlwinds. On the 29th of Apmil, 
1867, at 10 o'clock a. m., I was approaching Tuscaloosa, on the 
yton road, the general direction being east and west. | 
Weather was hot and —— while a perfect calm prevailed 
slight angular projection, like an inverted cone, at its lower 
I St saies 4 ascertained that it was at this time about 
five miles distant from me, and a calculation, based upon the 
estimated angles, fixed the elevation of its base above the sur- 
