"معاملات الجمعية الجغرافية في بومباي، من يناير ١٨٤٧ حتى مايو ١٨٤٩. تحرير السكرتير. المجلد VIII." [‎٣‎٣] (٤٩٦/١٣٦)

33
si*,
7 ma H
'honest
' tlle sa^
he
; aft ofa, r
^ heated
Very lowes t%
ncrease sto 1(s ,
f so ^ r apnj
S lts c °wse
onsoon,
'id drift
a S en de s®i
16 masses of «||
ollision wi
would,
1 other fluids, m
o a common t®
•e in the form I
ivel of
)rding to ci
ot now advert to
ns is more orb
^nsation,
nge of va
a#
en se *■ '■
sqa^
ordinary level, would press on all sides towards the focus of mini
mum resistance, and the pressure would be greatest on the densest
layers resting on the surface of the earth, where the circular motion
would assume an involute or helical direction, increasing in tempestu
ous gyrations as it approached the centre. For a continuance of the
whole process, it is equally apparent that this centripetal tendency of
the atmosphere at the base must be counterbalanced by a removal of
air at the centre, by means of a focal current in a vertical direction
at the point where the barometer is at its lowest range, and the stor-
my gusts cease to brush the surface in a horizontal direction, and cause
that portentous calm which, strange to say, is the very core of the
fiercest tempest. A rush of the ferial currents from the circumfer
ence towards the centre, would, even in a helical direction, restore a
loss of pressure of two inches in an hour’s time, and the vortical vio
lence would be quickly ended if some agency did not exist at the up
per parts of the focus capable of steadily withdrawing the ascending
stream of air. In fact, the true explanation of this last cause may
be considered as the key to the whole subject, but is a question that
can never, in all probability, he practically determined,—its solution
must alone rest on reasoning and analogy.
Height of the Rotatory Motion —It is more than two years since we
surmised that the circular motion of the atmosphere during great hur
ricanes extended to a much greater elevation than was generally ad
mitted. This opinion has been now most fully confirmed by the obser
vations made on Dodabetta, where the serial currents were speeding
round that part of the circle, at the height of nearly two miles
perpendicular from the level of the ocean, and at a distance of one
hundred miles from the focus, with a velocity of one hundred and nine
miles per hour. Consequently, it may reasonably be inferred that
far above this lofty peak the atmosphere was under the influence of
the storm. The centrifugal action, consequent on revolving motion,
would withdraw the atmosphere from the centre and throw it off to
wards the periphery. Thus, while a vast disc of atmosphere is in ro
tation at a level far above the surface of the earth, there must be cen-
njugal action at the upper part of the centre, where the atmosphere
ight, and a centripetal movement among the lowest and densest
strata, sweeping with vorticular violence to the focus ; the strength of
the latter being in the ratio of the former. The laws of hydrosta
tics, hydraulics, and pneumatics, may appropriately be referred to as