The Express.
London, England, 1861-02-18 00:00:00

TO TIM EDITOR OP Tilt EIPREIO3.

Ste,—A letter in the Times of this day, from Mr.
Jackson, of Hartlepool, not only requires some remarks
from me (as the Meteorological Officer acting under
authority of the Board of Trade), but seems to call for •
few sentences of practical information about a frequently
misunderstood fact—the rising of a barometer before and
d uring a northerly (north-west to north-easterly) gale.
Mr. Jackson' says that the barometer bad been "low,
with south-west winds, on Friday morning—began to rise,
and continued rising, with a decreasing temperature, Fri-
day, Saturday, and Sunday, from 24 hours before the
gale to 24 hours after." And if he had read the sixpenny
" Barometer Manual," published yearly since 1856, by
the Board of Trade, and circulated gratis in many direc-
tions, especially among the fishermen around Great
Britain an/Ireland, he would have known that the very signs
which be mentions coming after an unusually low barometer
and southerly wind indicated strong northerly gales.
In the morning of Wedeeeday, Feb. 6th, the !Ammeters (two,
Kew verified) at Nairn, in Scotland, were at 28.66—at Pen-
zance, only four days previously, two similar ones were at
30.80. From the Ist to the ith of February —a whole week
—the barometer not only continued falling, or oscillated
(always a bad sign), over all the British islands, bet it fell
remarkably low at some places. On Tuesday night, the sth,
it blew "a tremendous gale from the south-watt" at
Queenstown ; at Dover, the wind early on the 6th was re-
purted as 10, in force, from the &W. In South Kent it
was called "a hurricane "—and at sea, southward of Ire-
land, vemals bad • " south-wester" in full violence. Wed-
nesday and Thursday were quiet comparatively—here (not
so within • few hundred miles ; at Marseilles and elsewhere,
perhaps including the Black Sea), but on Friday the foretold
Northerly gale began to blow, and as it restored the level,
or equilibrium, of the atmosphere, of course it raised t►e
barometer.

Boma obervations in the Slapping Gazdte of the 14th
induced me to write a letter to the editor, in which was the
following passage t—" The barometer began to rim just
before the gale set in from the northward, Amin more
rapidly as it blew stronger. And why? Because the
polar current of wind was rushing, as a fluid current,
towers the place of low barometer, where a comparative
deficiency bad existed, which it not only filled up, but,
having once acquired impetus, or momentum, filled up to a
height exceeding that which is usual or normal at the sea
levelAnamely, about thirty inches." The previous fall of
the barometer with unusually high temperature expressed as
plainly as words could have done, " lloutherly wind with
rain" (" southerly " including southeast to south-westerly).
That wind, though it blew bard, did not restore the level
(or equilibrium) of the atmosphere, and therefore till the
polar current approached, the glass continued to fall, or
oscillated while low. Direeily the northerly wind's ap-
proach was felt the barometer began to rise—the thermo-
meter was already falling—and both thus moved for a time
In opposite directions, one rising for the direction of the
wind, while the other fell for its temperature.
The great practical difficulty in using • barometer le
avoiding the natural inclination to draw conclusions hastily,
without thinking enough of its foretelling properties, so
often insisted on in the Board of Trade " Manual," and the
more explanatory pamphlet, the " Barometer Guide."
The main em rents of de atmosphere polar and tropical
(taking them on • large scale) advance along the earth's
surface side by side in nearly opposite directions, more Or
lees superposed, or conflicting in every kind of combination,
and turning each other in all varieties of eddies (cyclones),
though usually in one way. While advancing northward
or southward they move also laterally (like a ship making
lee way) towards the east, their elasticity, fluid properties,
and different temperatures (voter influence and eloctricity
of course their roainsprimpi) occasioning all the varieties of
weather, all the alternations and degrees of vapour, fog,
rain, snow, hail, and cloud that we experience.

•
The gales of the Mb, Nth, and 9th of this month were
eyeleale combination. Ose cyclone, of which the osn•
triad area bore northwestward from Nairn, was of large
extent. Its southern half was checked and temporarily
overborne by another advancing rapidly from the south-
westward, which combined with and augmented the strength
of the polar current that on Friday, Saturday, and Sunday
(10th) swept acmes the north sea, west of Europe, aad
beyond the west of Ireland, much farther and wider than
the extent of the " Royal Charter" storm.
Widely extended and general irregularities of the atms•
phere— such as were shown by ir.struments before the Rays
Charter, the Whiteuntkle, the St. Kilda, and other storms
—are easily noticed, and are certain to be followed by =WO
or lass strength of wind, although net is all, or even many
plains, because currents-of wind, like those of water, circu-
late, intermix, or follow one another, moving swiftly in
sons breadths, slowly in others, scarcely at all in or near
their respective centres of circulation. Hence some places
escape the violence of • storm, whilst others, ova we
Itiom, feel its full fury.
Elaborate and complicated as may be the scientifio re-
searches of meteomlogy, the practical use of its resulta is
happily most simple, and available to any one who will read
brief instructions, notice ordinary weather glasses, and ob.
serve changes in the heavens.
Feb. 16. ROB. FITZ ROY.