24 + On the Spirality of Whirlwinds. 
the whirling body ; for the reason that the rotation here is pro- 
portionally 1 more active and intense, being impelled by the ag- 
gregated pressure and momentum of the more outward portion 
of the whirlwind as it converges from its larger area, on all sides, 
by increasingly rapid motion, into the smaller area of ascending 
rotation.* ‘That this interior ae of the wis resembles an 
we Accessions caused by cireumjacent contact and pressure are 
constintly accruing to the whirling body, so long as its rotative 
energy is maintained. A correlative diffusion from its ascending 
portion must necessarily take place, towards its upper horizon ; 
and this is often manifested by the great extent or accum ulation 
of cloud which results in this manner from the action of the tor- 
nado. In other words, there is a constant Seas from the 
whitling body in the direction of least resistance. 
SY he spirality of the rotation and its ca to the hori- 
zon, in the great portion of the whirl which is wig sa its as- 
cending area, is not ordinarily subject to direct observation. Nor 
is the. outline or body of the more outward portion of vem aie 
wind = all visible, otherwise than in its effects. 
eous vortices the axial spiralities of the aap oar and 
pat portions are in reverse direction to those in the a 
phere, the descending spiral being nearest to the axis of ne vor- 
tex. Hence, lighter “bodies and even bubbles of air are often 
forced downward i in the water, in the manner in which heavier 
bodies are forced upwards in the atmosphere 
e foregoing is simply a statement of rebate eter I have 
derived from a long course of observation and in It does 
not include the partial and imperfect exhibitions ‘of whirlwind 
action, which often occur; nor the various movements and phe- 
nomena which are collaterally associated with tornadoes and 
whirlwinds, some of which are of much significance. 
* The law of i increment in {be eYalocity of the lap hese ¥ it gradually con- 
bodies when d tated fe a graduall 
wn or ed nearer and nearer, in their involute course ;—the line of focal or 
centripetal e, thus sweeping egual areas in times, at whatever diminu- 
tion of distance freak i center ; except as the aes yey be effected in degree 
by resistan er bodies. uch resistance is 0 e effect i ina tornado, 
