The Hurricane Guide | Page 4

the quarter from which the N.W. current is advancing laterally, also
S.W., he will find that with a rising barometer and N.W. wind the
current passes him from right to left. Now the two classes of
phænomena are identical, and it would not be difficult to show that, had
we an instance of a rotatory storm in the northern hemisphere moving
from N.W. to S.E., it would present precisely the same phænomena as
to the direction of currents passing from left to right and from right to
left with falling and rising barometers, increase and decrease in the

force of the wind, &c., as the oppositely directed aërial currents do
which pass over western central Europe.
In the absence of direct evidence of the production of a revolving storm
from the crossing of two large waves, as suggested by Sir John
Herschel, although it is not difficult to obtain such evidence, especially
from the surface of the ocean, the identity of the two classes of
phænomena exhibited by the storms and waves as above explained
amounts to a strong presumption that there is a close connexion
between them, and that a more minute investigation of the phænomena
of atmospheric waves is greatly calculated to throw considerable light
on the laws that govern the storm paths in both hemispheres. The
localities in which these atmospheric movements, the waves, have been
hitherto studied, have been confined to the northern and central parts of
Europe--the west of Ireland, Alten in the north of Europe, Lougan near
the Sea of Azov, and Geneva, being the angular points of the included
area. It will be remarked that the greatest portion of this area is inland,
but there is one important feature which the study of the barometer has
brought to light, and which is by no means devoid of significance, viz.
that the oscillations are much greater in the neighbourhood of water,
and this appears to indicate that the junction lines of land and water
form by far the most important portions of the globe in which to study
both the phænomena of storms and waves. It is also very desirable that
our knowledge of these phænomena should, with immediate reference
to the surface of the ocean, be increased, and in this respect captains
and masters of vessels may render essential service by observing and
recording the state of the barometer, and direction and force of the wind,
several times in the course of the day and night;[3] and when it is
considered that the immediate object in view is one in which the
mariner is personally interested, and one in which, it may be, his own
safety is concerned, it is hoped that the keeping of a meteorological
register having especial reference to the indications of the barometer,
and force and direction of the wind, will not be felt as irksome, but
rather will be found an interesting occupation, the instruments standing
in the place of faithful monitors, directing when and where to avoid
danger, and the record furnishing important data whereby the
knowledge of general laws may be arrived at, having an essential

bearing on the interests of the service at large.
CHAPTER III.
OBSERVATIONS.
In sketching out a system of observation having especial reference to
atmospheric waves and rotatory storms, regard has been had--first, to
the instruments that should be used, the observations to be made with
them, the corrections to be applied to such observations, and the form
of registry most suitable for recording the results: second, to the times
of observation: third, to the more important localities that should be
submitted to additional observation: fourth, to peculiar phænomena
requiring extraordinary observations for their elucidation: and fifth, to
particular seasons, when the instruments should be watched with more
than ordinary care.
The more important objects of observation having especial reference to
atmospheric waves are those points which have been termed crests and
troughs. These are simply the highest and lowest readings of the
barometer, usually designated maxima and minima, and should for the
object in view receive particular attention. Whenever there is reason to
believe that the barometer is approaching either a maximum or
minimum, additional observations should be resorted to, so as to secure
as nearly as possible the precise time as reckoned at the ship, with her
position, of its occurrence, as well as the altitude of the mercurial
column at that time and place. By means of such observations as these
on board several ships scattered over the surfaces of our great oceans,
much valuable information may be accumulated of a character capable
of throwing considerable light on the direction in which the lines of
barometric maxima and minima stretch, and also a tolerably accurate
notion may be formed of their progress, both as regards direction and
rate. In immediate