'Transactions of the Bombay Geographical Society, from January 1847 to May 1849. Edited by the Secretary. Volume VIII.' [‎5] (106/496)

5
To render the following observations more intelligible to general
readers, it may be well to convey some idea of what is meant by a
Rotatory Gale. It has been ascertained that during grea't storms or
typhoons, within, or near to, the tropics, the wind blows in a circuit
round a moving focus ; and that the force increases, from light winds
or a moderate breeze at the periphery, till near the middle it acquires
all the violence and character of the hurricane. Perhaps one of the
most extraordinary features in the whole history of storms is the fact
of the very centre being occupied by a calm space of ten to twenty
miles in diameter, around which the wind revolves with overwhelming*
impetus. It is also found that the barometer indicates diminished at
mospheric pressure, beginning at the exterior of the stormy circle and
increasing towards the focus, where the amount of depression of the
mercurial column has frequently exceeded two inches. The diameter
of the area over which the wind rotates in conformity with the
circle, is often 600 or 700 miles, but it is only within 100 or 150
miles of the centre that the force is equivalent to a typhoon or hurri
cane. The direction of the rotation is always the same in the same
hemispheres; that is, in the northern, S.E.N.W., or with the hands
of a watch; and in the southern, N.E.S.W., or in the contrary way.
While a vast disc of atmosphere is thus revolving on its centre, and
in leality forming a gigantic whirlwind, the whole moves onward
along a certain line of progression, from which it seldom diverges
beyond a few points, and which runs in a westerly direction from the
equator towards the poles, being N.W. in the northern, and S.W. in
the southern, hemispheres. Thus a person looking westward, on the
equator, at Sumatra, would find the storms on his right curving
towards India or the Bay of Bengal, and on his left rushing S.W. co
in the direction of Mauritius. It is impossible to notice, even in a
brief manner, all the important features of gyratory storms, such as
the incessant rain, electrical discharges, and confused sea, raised by
the “ contending winds.”
From a careful examination of all the particulars connected with
the late Gale on the Malabar coast, I am fully satisfied that it was a
ievolving and progressive typhoon, obeying the laws which have just
been alluded to as governing such phenomena in the northern hemis
phere, with this peculiarity, that its path, instead of being N. West-
eily, like those traced by Mr. Piddington in the southern part of the
Arabian Sea, was much more northerly, and nearly following the
inc of coast from Cape Comorin to Kurrachee. The central track