The Sun.
London, England, 1860-04-11 00:00:00

111.ETEOROLOG 'CAL SOCI_ETY.

At the last meeting of this society a paper was
read on "Duet Storms, Dust Columns, and the
Simoona or by H. Cook,
Poisonous Winds of India,"
M.D. The author remarked that there are certain
days in which, however hard and violently the wind
may blow, little or no dust accompanies it, whilst
at other times every little puff
of air or current of
wind raises up and carries with it clouds of dust,
and at these times the individual partiele.s of sand
appear in such an electrified condition that they
are even ready to repel each other, and are conse-
quently disturbed from their position and carried
into the air with the slightest current. To so great
an extent does this sometimes exist that the atmos-
phere is positively filled with dust, and when ac-
companied by a strong wind nothing is visible at a
few yards, and the sun at noonday is obscured;
This condition is evidently accumulative; it in-
creases by degrees until the climax is reached,
when, after a certain time, usually 24 hours, the at-
mosphere is cleared, and equanimity is restored.
Dust columns appear under a similar condition of
electrical disturbance or intensity. On calm quiet
days, when hardly a breath of air is stirring, and the
sun pours down his heating rays with full force,
little circular eddies are seen to arise in the atmo-
sphere near the surface of the ground. These in-
crease in force and diameter until a column is formed
of great height and diameter, which usually remains
stationary for some time, and then sweeps away
across the country at great speed, and ultimately,
losing the velocity of its circular movement, dis-
solves and disappears. The author had seen in the
valley of Muigochav, which is only a few miles
across, and surrounded by high hills. on a day when
not a breath of air stirred, 20 of these columns ;
these seldom changed their places, or but slowly
moved across the level tract, and they never inter-
fered with each other. The author then spoke of
the simoom, that deadly wind which occasionally
visits the deserts of Cntcbee and Upper Scinde,
which is sudden and singularly fatal in its occur-
rence, invisible, intangible, and mysterious—its
nature alike unknown (as far as the author is
aware) to the wild and untutored inhabitant of the
country it frequents as to the European man of
science; its effects only are visible, its presence
made manifest in the sudden extinction of life,
whether animal or vegetable, over which its influ-
ence has extended. The author gives the results
of his information respecting the simoom as fol-
lows :-1. It is sudden in its attack. 2. It is
sometimes preceded by a cold current of air. 3.
It occurs in the hot months (usually June and
July). 4. It takes place by night as well as by
day. 5. Its course is straight and defined. 6. Its
passage leaves a narrow knife-like track. 7. It
burns up or destroys the vitality of animal and
vegetable existence in its path. 8. It is attended
by a well marked sulphurous odour. 9. It is de-
scribed as being like the blast of a furnace, and the
current of air in which it passes is evidently greatly
heated. 10. It is not accompanied by dust, thun-
der, or lightning ; and concludes his paper by say-
ing, "If it, then, be neither a phase of sunstroke,
lightning, malaria, nor miasmata, in a concentrated
form, what is it ? or to what is it to be referred P"
A paper was then read by Mr. G. A, Rowell on
the " Great Storm in Wiltshire on December 31,
1859." The accounts in the public papers describe
the storm as a whirlwind. 11'..`r. Rowell had care-
fully examined its track, and not only found no
proof of a whirling of the wind, but that many of
the effects of the storm could not have been pro-
duced by cuirents of air moving, either in circles or
direct. He believed the violence of the storm to
have been the result of a rarefaction or partial
vacuum in the storm cloud, and the destructive
effects were produced by the expansion of the
air within or beneath the buildings, &c., owing
to the diminution of atmospheric pressure as
the cloud passed over, or by the rush of
air into the rarified space as it passed onward.
Mr. Espy and Mr. T. Hopkins ascribe such upward
currents of air as might have caused such a storm
to the expansion of the air from the disengagement
of latent heat by the condension of vapour. It may
be objected to this view, that the heavy rain which
accompanied this storm must have been the result
of such an enormous condension of vapour, that the
heat disengaged by it must have put a stop to all
further condension at the time, whereas the like
heavy rain accompanied the storm throughout. The
theory advanced by Mr. Rowell is that evaporation
is produced by the minute particles of water being
buoyed up into the air by their coatings of electri-
city when in their agglomeration into drop's of rain,
as the surface of the drops is much less than that of
the aggregate surfaces of the vapour of which they
are composed, a vacuum is created on the instant
from formation of every raindrop by the passing
away of the surplus electricity. Consequently a
rarefaction or partial vacuum would result from
the formation of rain in accordance with its extent,
and so long as it might continue. The storm began
near Calne, and continued in the general direction
of the wind over about 11 miles, the width, as marked
by its destructive effects, being from 100 to 400
yards. The great violence did not last more than from
three to five minutes at any one place. The fall of
rain was enormous, with thunder and lightning, and
the clouds were so low as to seem to sweep the
ground. It was accompanied by a terrific roaring
noise, and the hailstones fell of extraordinary size
and form. A vast number of trees were blown
down, and much damage done by the wind.
Amongst other effects, the slates were taken off roofs
on their leeward side; the roof of a shed, stoutly
built of elm timber, and covered with blue slates,
the estimated weight of which was four tons, was
lifted off the walls and deposited on the ground
quite clear of them, without a single brick being
disturbed. 'I his shed was protected from the effects
of the wind by a much loftier building about 25
yards from it on the windward side. A waggon
weighing one ton two hundredweight, with a hun•
dred weight of hay in it, was lifted right over a hedge,
to clear which it must have been carried more than
eight feet in height. The under surface of this
waggon was not more than 66 square feet: a pres-
sure of 39 pounds to the square foot would not have
lifted the waggon from the ground, even if the wind
could have blown so as to act perpendicular to the
bottom of it. Other facts were mentioned to show
the effects could not have been produced by a direct
wind, and amongst them was that of the two
ends of (I, garden wall being both blow iuyskrds,