We have now presented a theory of the weather, which accounts for many
prominent phenomena, a few of which we shall enumerate. It is an
observed fact, that in all great storms electrical action is more or
less violent, and that without this element it seems impossible to
explain the velocity of the wind in the tornado, its limited track, and
the formation of large masses of ice or hail in the upper regions of the
atmosphere. It is also an observed fact, that the barometer is in
continued motion, which can only be legitimately referred to a change in
the weight of the atmospheric column. This we have explained as due to
atmospheric waves, caused by the greater velocity of rotation of the
external ether, as well as to the action of the three great vortices.
These causes, however, only partially produce the effect--the greater
portion of the daily oscillations is produced by the action of the great
radial stream of the solar vortex, as we shall presently explain. It is
an observed fact, that, although the storm is frequently violent,
according to the depression of the barometer, it is not always so.
According to the theory, the storm will be violent, _ceteris paribus_,
on a line of low barometer, but may still be violent, when the contrary
obtains. Another fact is the disturbance of the magnetic needle during a
storm. Storms are also preceded generally by a rise in the thermometer,
and succeeded by a fall; also by a fall in the barometer, and succeded
by a rise. It is also well known, that hurricanes are unknown at the
equator, and probably at the poles also. At all events, they are rare in
lat. 80d, and, according to Capt. Scoresby, storms are there frequently
raging to the south, while above, there is clear sky and fine weather,
with a stiff breeze from the northward. The greater violence of storms
in those regions where the magnetic intensity is greater in the same
latitude, the probable connection of peculiarities in the electric state
of the atmosphere with earthquakes, and the indications of the latter
afforded by the magnet; the preponderance of westerly winds at a great
elevation in every latitude on the globe visited by man; and the
frequent superposition of warm layers of air above cold ones at those
elevations, are all facts worthy of note. And the connection of cirrus
clouds with storms, as well as with the aurora, indicates that the
producing cause is external to the atmosphere, and gradually penetrates
below. The theory fully explains this, and is confirmed by the fantastic
wreathings and rapid formation of these clouds in straight lines of a
hundred miles and upwards. But time would fail us in pointing out a
tithe of the phenomena, traceable to the same cause, which keeps our
atmosphere in a perpetual state of change, and we shall only advert to
one more peculiarity of the theory. It places meteorology on a
mathematical basis, and explains why it is that a storm may be raging at
one place, while in another, not very remote, the weather may be fine,
and yet be dependent on the position of the moon.
That the moon has exerted an influence on the weather has been the
popular creed from time immemorial; but, ignorant of the mode in which
this influence was exerted, men have often been found who have fostered
the popular belief for their own vanity or advantage; and, on the other
hand, philosophers have assailed it more by ridicule than by argument,
as a relic of a barbarian age. Not so with all; for we believe we are
not wrong in stating, that the celebrated Olbers compared the moon's
positions with the weather for fifty years, before he gave his verdict
against it. He found the average amount of rain at the perigee about
equal to the amount at the apogee, as much at the full as at the change,
and no difference at the quadratures. But this fact does not throw a
feather in the scale by which this theory is weighed. Popular opinions,
of remote origin, have almost always some foundation in fact, and it is
not much more wise to reject them, than to receive them. The Baron Von
Humboldt--a man possessing that rare ingredient of learning, a practical
common sense--observes: "That arrogant spirit of incredulity which
rejects facts, without attempting to investigate them, is, in some
cases, more injurious than an unquestioning credulity."[22] If a popular
belief or prejudice be absurd, its traditional preservation for a
thousand years or more may very well account for the absurdity.
The present system of astronomy still retains the motley garniture of
the celestial sphere, as handed down from the most remote antiquity; and
granting that ages of ignorance and superstition have involved the
history of the different constellations in a chaos of contradictory
traditions, there is no doubt at the foundation some seeds of truth
which may even yet emerge from the rubbish of fable, and bear fruit most
precious. That the zodial[23] signs are significant records of something
worthy of being preserved, is prejudice to deny; and we must be allowed
to regard the Gorgons and Hydras of the skies as interesting problems
yet unsolved, as well as to consider that the belief in lunar influence
is a fragment of a true system of natural philosophy which has become
more and more debased in postdiluvian times. Amongst those who have not
summarily ignored the influence of the moon, is Toaldo, a Spanish
physicist, who endeavored to show the connection between the recurrence
of warm and cold seasons, and the semi-revolution of the lunar nodes and
apogee, and proposed six of those periods, or about fifty-four years, as
the cycle in which the changes of the weather would run through their
course. According to the present theory, it is not likely such a cycle
will ever be discovered. There are too many secular, as well as periodic
influences combining, to produce the effect; and the times are too
incommensurable. Lately, Mr. Glaisher has presented a paper to the Royal
Society, giving about fourteen years from observation. Others have
lately attempted to connect the changes of the seasons with the solar
spots, as well as with the variations of the magnetism of the earth, but
without any marked result.
It may, however, be urged, that if the sidereal period of the moon be
approximately a cycle of change, it would have been detected long ago.
One reason why this has been so long concealed, is the high latitude of
the observers. Spain, Italy, and Turkey, are better situated than other
European countries; but the scientific nations lie further north; and
from these the law has gone forth to regulate more southern lands. In
the United States, particularly in the great plains of the west, the
weather can be better compared; not only on account of the latitude
being more favorable, but also on account of the greater magnetic
intensity of the western hemisphere.
It must also be remembered that there are in latitude 40d, five or six
distinct passages of the disturbing cause in one sidereal period of the
moon. If two of these periods are drawn closer together by the change of
the elements, the interval between two others must necessarily be
increased. Besides, the effect produced is not always the same, for
reasons already adverted to. One vortex may be more violent one month,
or for a few days in one month, while another may be more active the
next. It may also happen that for several successive passages, the
passage shall be central in one latitude, while two or three degrees
north or south, another place shall be passed by. In different months
and in different years, as well as in different seasons of the year, the
energy of the ether may be augmented or diminished. But it may be said,
that, supposing the theory true, if its indications are so uncertain, it
is of little value. By no means. It is true there are many things to be
inquired into; but it is a great thing in this science to be able to
take the first step in the right direction,--to find even the _key_ of
the portal. It is a great stride to be able to say, a storm may happen
at such a time, but cannot happen at another; that a storm, when raging,
will go in this direction, rather than in that; that it will be central
here, and less violent yonder; and when we consider its bearing on
astronomical and other science, it is difficult to exaggerate its value
to the world at large.
Again, it may be said that rain, and cloudy days, and fresh breezes, and
even strong winds, sometimes occur, when the vortices do not pass
centrally. This is true; yet only indicating that where the vortices are
central, an unusual disturbance is taking place. But there is another
cause, which was purposely omitted in considering the prominent features
of the theory, in order not to encumber the question with secondary
influences. By referring to Fig. 3, section 1, we see that the lateral
vortices of the globe are continually passing off to the southward, in
the northern hemisphere, in a succession of dimples, and continually
reforming. We will now represent this mode of action in profile, as it
actually occurs in the illustration we have used.
The vortex passing off from O, (Fig. 20,) although it does not actually
reach the surface of the atmosphere, affects the equilibrium of the
ether, and, for a short distance from the parent vortex, may cause an
ascensional movement of the air. If to this is conjoined a northerly
wind from the vortex, a band of clouds will be produced, and perhaps
rain; but violent storms never occur in the intervals, except as a
steady gale, caused by the violence of a distant storm. Thus, it will
frequently be noticed that these vortices are flanked by bands of
clouds, which pass southward, although the individual clouds may be
moving eastward. Hence, instead of disproving the theory, they offer
strong evidence of its truth; and could we view the earth from the moon
with a telescope, we should no doubt see her beautifully belted.
[Illustration: Fig. 20]
But it may be again asked, why should not the weather be the same
generally, in the same latitude, if this theory be true? If the earth
were a globe of level land, or altogether of water, no doubt it would be
similar; but it must be remembered, that both land and water are very
unequally distributed: that the land is of varying extent and
elevation--here a vast plain, far removed from the ocean, and there a
mountain chain, interposing a barrier to the free course of the
atmospheric currents; sometimes penetrating in full width into the
frigid zone, and again dwindling to a few miles under the equator. One
very important distinction is also to be remarked, in the superficial
area of the different zones, reckoning from the equator, and taking the
hemisphere as 100 parts:
Frigid zone 8 parts.
Temperate " 52 "
Torrid " 40 "
For as the time of rotation in every latitude is the same, the area to
be disturbed in the same time, is less in high latitudes, and there a
greater similarity will obtain, _ceteris paribus_. In lower latitudes,
where both land and water stretch away for thousands of miles, it is not
wonderful that great differences should exist in the electrical and
hygrometric state of the air.
The summer of many countries is always dry--California for instance. In
winter, in the same country, the rains are apparently incessant. This of
course depends on the power of the sun, in diverting the great annual
currents of the atmosphere. As long as the dry north-west trade sets
down the coast of California, the circumstances are not favorable for
giving full development to the action of the vortices. When the trade
wind ceases, and the prevailing winds come from the south, loaded with
vapor, the vortices produce storms of any magnitude; but (and we speak
from two years' observation) the passages of the vortices are as
distinctly marked there in winter time, as they are in the eastern
States; and in summer time, also, they are very perceptible. The same
remark applies to Mediterranean countries, particularly to Syria and
Asia Minor; although the author's opportunity for observing lasted only
from April to December, during one season. If we are told it never rains
on the coast of Peru, or in Upper Egypt, it does not seriously militate
against the theory. The cause is local, and the Samiel and the sand
storm of the desert, is but another phase of the question, explicable on
the same general principles. From the preceding remarks it will be seen,
that in order to foretell the character of particular days, a previous
knowledge of the weather at that particular place, and for some
considerable time, is requisite; and hence the difficulty of laying down
general rules, until the theory is more fully understood.