Coming back now, to a consideration of the course and functions of the
counter-trade after it leaves the northern limit of the surface-trades, we
find it curves to the eastward and gradually assumes about an E. N. E.
course, and becomes a W. S. W. current where it crosses the line of no
variation, and continues on until it passes off over the Atlantic; and
this course and curve is analogous to what may be found true of the
counter-trades every where. It is best illustrated by the course of all
the storms (in the American sense of the word, as distinguished from
thunder showers and other brief rains), which have been traced north or
south of the limits of the trades. It was found by Mr. Redfield in most of
the storms investigated by him, which originated within, or north of the
tropics.
Doubtless it was the actual course of the others, and that the
investigation was imperfect. All the great autumnal, winter, or spring
storms which have traversed the whole or any considerable portion of the
territory of the United States, east of New Mexico, which have been
investigated by Professors Espy, Loomis, Redfield, or others, have been
found to follow this course. A storm which passed over Madeira, appears
from the investigations of Colonel Reid to have followed the same law of
curvature.
And so, doubtless, did another which he has described as passing over the
Levant. The storms which supply the winter rains of California and Utah,
reach them by this law of curvature and progress, after the northern
limits of the trades have descended to the south with the sun, so that the
counter-trades of the Pacific may descend to the surface and curve in upon
them. But the absence of a concentration of the counter-trade, and its
deficient action because of its passage over mountain ranges, and their
location so near the northern limit of the trades that their storms can
not expand and become extensive, as well as their weaker magnetic
intensity, prevent their storms from becoming violent, and their supply of
rain is not large and much of it falls in showers. The same is true of the
Barbary States, of Syria, and Persia, and of Southern Europe; and indeed
of all the countries of the globe which lie between the winter and summer
extreme limits of the surface-trades, and without the limits of the two
concentrated counter-trades. Enough appears in the writings of the
meteorologists of Europe to show, that their long continued rains, which
are analogous to our storms and are _preceded by the formation of the true
cirrus of the counter-trade_, follow the same great law of curvature and
progress; although the presence of the Gulf Stream with its mass of south
polar waters on the western side of the British Islands, Denmark, and
Norway supplies them with showers, and fogs, and cumuli from the west and
north-west, and makes the mean of the surface winds of their storms
somewhat variant from ours. A like law reversed prevails in the southern
hemisphere. The storms of New Holland and the Indian Ocean, south of the
limits of the trade, curve to the eastward and travel about south-east,
their _south-west_ being a _clearing off wind_ as our _north-west_ is, and
_precisely similar in all its other characteristics_, where the relation
of magnetic intensity is the same.
The storms of the Pacific on the S. W. coast of South America, in like
manner travel to the S. E., flooding the western slopes of the mountain
ranges with rain, and aggravated by the intensity of the magnetic currents
at the extremity of the continent in a high latitude, meet the mariner in
the face as he emerges from under the lee of the land and attempts to pass
the Horn. It will ultimately be shown that the precipitation which takes
place, as the storms and counter-trades pass north and east in the
northern hemisphere and south and east in the southern hemisphere, is
owing less to cold than increased magnetic intensity. And all this is the
result of one great uniform law, existing every where, varying in its
phenomena only in consequence of the difference in volume, and
magneto-electric intensity of the portions of the counter-trade, as of the
surface-trade at different places, and the different magnetic intensity of
the local perpendicular and circular currents of the earth over which they
pass, at different periods and at different points.
Mr. Redfield and Lieutenant Maury have assumed that our S. W. current
comes from the Pacific Ocean. Aside from the adverse evidence which the
investigations of the former in relation to the course of the West Indian
storms, and their curving over the continent, furnish to the contrary, and
that which has herein before been stated in relation to the law of
curvature, it is obvious they are mistaken, for another and conclusive
reason.
In order to reach us from the Pacific in a direction from S. W. to N. E.,
it must pass the table lands and mountain ranges of Mexico and New Mexico,
and it would supply them bountifully, even if it did not thereby leave us
comparatively rainless and sterile. Every where currents passing from the
ocean _over mountain ranges_ part with a large share of their moisture.
Thus the counter-trade which curves over the Andes and over Peru, is
deprived of its moisture and leaves the western coast rainless. So in
degree of the counter-trade which curves over the Himalaya and Kuenlon
Mountains, and from there passes over the Desert of Cobi, to the north and
east--it is deprived by those elevated ranges of its moisture. So the
mountains on the south-western coast of South America are drenched with
rain, while Patagonia, which lies on the east of them is comparatively
dry. And so of every other country similarly situated.
Now the mountain ranges and table lands of Mexico are not thus supplied
with moisture. For the space of four months in Southern and less in
Northern Mexico, and in summer, and while the belt of the tropics is
extended up over them, they have rain and in daily showers which _travel
up from the south_, indicating the course of the counter-trade. (See
Bartlett's Personal Narrative, vol. ii. p. 286.) At other seasons, and
while we are bountifully supplied, they are dry. In short, there are no
two portions of the earth that differ more widely in regard to their
supply of moisture, and all their climatic characteristics and relations.
It is therefore, according to all analogy, impossible that our
counter-trade should come from the South Pacific across the continent and
below 35 deg., and in this also those gentlemen are mistaken.
Messrs. Espy and Redfield recognizing the existence of "a prevailing" S.
W. current, but considering the surface-winds beneath it as the principal
actors in producing the atmospherical conditions and changes, have
attributed no office to that current, except that of giving direction and
progression to our storms. This is their great mistake. It plays no such
unimportant part in the philosophy of the weather, as we have already
incidentally seen, and will proceed still further to consider.
_All our storms originate in it._ This we may know from analogy.
_Where there is no counter-trade, outside of the equatorial belt of rains,
and within influential distance of the earth, there are neither storms nor
rain._ So, when, as we have seen, the concentration of the volume of
northern counter-trade in the West Indies, gathered by the hauling of the
S. E. trades more from the east, as they approach the central belt,
diminishing the volume of the counter-trade over the North Atlantic, the
calms and drought of the horse-latitudes are found. And when the
counter-trade is small in volume and weak in intensity, by reason of the
fact that the surface-trades from the opposite hemisphere which constitute
it, formed upon land where evaporation was small, as upon Southern Africa
and New Holland, or formed where the magnetic intensity was weak, or
passed over mountain ranges in their course, the annual supply of rain,
the ranges of the barometer, and the alternations of atmospheres
conditions are remarkably less.
We have already seen where the rainless portions of the earth are, and why
they are so; because those lying north of the northern limit of the
equatorial rainy belt were yet too far south to be covered by the line of
extra-tropical rains; or in other words, too far south to be uncovered by
the surface N. E. trades and the longitudinal magnetic currents, and to be
covered by the counter-trades in contact, or nearly so with the earth, and
influenced by the perpendicular north polar magnetic currents. Thus we
have seen that the rains of Southern Mexico were summer rains, due to the
northern extension of the equatorial rainy belt; those of California were
winter rains, due to the southern extension of the extra-tropical rains
following the N. E. surface trades. We have also briefly alluded to the
fact that either side of the equatorial rainy belt, evaporation is going
on for months under a vertical sun, without precipitation--unless it be
from an occasional brief storm of great intensity which originates in that
belt at the line of it, and passing on in the counter-trade, reverses, for
the time being, by its concentrated and powerful action, like a magnetic
body introduced into the field of another magnet, the surface-trades. Mere
evaporation then, does not produce the storm, or shower, or rain, where
most active in the dry torrid zone. It may be said that those dry portions
are, for the time being (as the rainless portions of the earth are
continually), within the operation of the surface-trades, and that
therefore the evaporated moisture is carried away by them toward the
equatorial rainy belt. Precisely so; but why carried away? Why should it
not condense, occasionally, at least, and drop the rain as it passes
along, if a great supply of moisture from excessive evaporation could
furnish rain. Perhaps it may still be said it is going from a cold to a
warm section. This is not true, as we have shown.
But, it may be said that the rainless regions at any rate receive no
moisture, and therefore can not supply any by evaporation. This would not
meet the case, as it would still be true that when the rainy belt has left
a given spot, the dry weather sets in with excessive evaporation, and the
north-east trades in summer, blowing from the countries lying north of the
rainless regions, and which have been supplied during the interval by the
extra-tropical rains, and are loaded with evaporation, are passing over
the rainless regions on their way to enter the central belt. So blow the
N. E. trades from the Mediterranean, and the Barbary States _over the
Desert of Sahara_ and into the rainy belt south of it; but drop no
moisture on their way, because exposed to no magnetic currents of an
opposite polarity.
But it is not true that all the rainless regions are without evaporation.
Egypt is an exception. The annual freshets of the Nile saturate its
central valley, and vast reservoirs of water are saved from it and let out
over its surface, and it all evaporates, but produces no rain. And so are
large quantities turned aside and scattered over the bottom lands of
Northern Mexico, and other countries, during the dry season, and their
evaporation furnishes no rain. Hygrometers and dew points are of no
consequence there--nor are they of any, on either side of the rainy belt,
where six perpendicular feet of moisture is evaporated in six months.
Again we have alluded to a strip of coast on the Pacific west of the
mountain ranges of South America, lying partly in Peru, partly in Bolivia,
and partly in Northern Chili, which, although long and narrow, washed by
the broad Pacific Ocean, is without rain. South America has no other
_wholly_ rainless region, so far as is known. A part of this region would
lie between the equatorial belt of rain, and the southern extra-tropical
one, and never be covered by either; but the volume of N. E. trades from
the Atlantic, although from the make of the land not concentrated to so
great an extent as the volume of S. E. trade on the north, and therefore
not so liable to hurricanes and other violent storms, is yet sufficiently
so to carry the southern line of the equinoctial rainy belt down in winter
to the summer line of extra-tropical rains, and give a supply of rain to
all the continent--leaving no strictly rainless region south of the
equatorial rainy belt and east of the Andes. Those mountains, however,
present a barrier to its south-western progress which it doubtless passes
to some extent, but deprived of its moisture, and unable to supply the
rainless coast region of Peru, Bolivia, and Northern Chili. There is,
therefore, a portion of this rainless line of coast which is within the
region of extra-tropical rains, over which a portion of the N. E. trades
of the Atlantic, as a counter-trade, should or do, curve, and where there
should therefore be extra-tropical rains. It is washed by the Pacific, an
evaporating surface, and westerly and south-west breezes are drawn in from
that ocean over it. Why then is it rainless? The only reason which can be
assigned why rain does not fall there is that the high mountain ranges of
the Andes intercept and perhaps in part divert the counter-trade, and
deprive that portion of it which passes them, of its moisture, by that
reciprocal action of opposite polarities which takes place whenever and
wherever the trade approaches so near the earth; and it curves over the
narrow line of coast with the feeble condensation, and imperfect forms,
and varied coloring which mark so peculiarly the rainless clouds of that
region. (See Stewart's Journal of a Voyage to the Sandwich Islands, page
72.)
Again, it is estimated, and on reliable data, that twelve perpendicular
feet of water are annually evaporated from the surface of the Red Sea,
between Nubia on one side, and Arabia on the other; yet they are both
rainless countries, except so far as the inter-tropical belt of rains
extends up on to a small portion of them. The moisture of evaporation,
floated up from a surface covered by the surface-trade is invariably so
combined as to remain uncondensed till it has passed south into the
equatorial rainy belt, and over to the opposite hemisphere, and been
exposed to the currents of an opposite magnetism.
Again, the N. E. trades extended up in summer over the Mediterranean Sea,
an evaporating surface, blow over the Barbary States in June and July, but
furnish no rain. And so of the S. E. or N. E. trades which blow over
Brazil and other countries in the absence north or south of the tropical
belt of rains.
It is obvious from these facts--and more like them might be cited--that
mere evaporation, however copious or long continued, does not make the
storm or shower in the locality where it takes place, and _without the
existence and influential agency_ of a counter-trade; and that _reciprocal
action_, whatever it may be, that takes place _between it and the earth_.
Again, our own experience is conclusive of this. We have no surface-trade
north of 30 deg., and yet a long drought and great evaporation may follow a
wet spring. Belts of droughts and frequent rains occur every year in
different portions of the country side by side, and _the dividing line
follows the course of the counter-trade_, and is sometimes distinctly
marked for weeks. When a change occurs in the counter-trade, whether from
causes existing there or the influence of terrestrial magnetism (in
relation to which we shall inquire hereafter), showers form or storms come
on: until it does they will not. Efforts at condensation will occasionally
appear, but they will be feeble and ineffectual, and occasion a repetition
of the axiom that "all signs fail in a drought." And we may know it from
direct observation.
The first indications of a storm, and of most if not all showers, are
observable in the counter-trade. These indications, so far as they are
visible, are of course to be looked for in the west; although the
direction and character of the surface-winds are often indicative of these
changes when not visible at the west as we shall see.
The indications are those of condensation, and vary very much in different
seasons of the year. It is not my purpose in this place to examine them
particularly. They will be alluded to hereafter under the head of
prognostics. Suffice it now to say, then, that whether it be the long
threads or lines of cirrus which occur in the trade in the winter after a
period of severe cold, following the interposition of a large volume of N.
W. cold air and the elevation of the counter-trade; or the forms of cirrus
which occur at other times and other seasons; or whether it be the
ordinary bank at night-fall, or the evening condensation which makes the
"circle" around the moon, or the morning cirro-stratus haze which
gradually thickens, passes over and obscures the sun, all which may be
followed by the easterly scud and winds: they are alike condensation in
the trade, the advance or forming condensation of a storm or showers.
The state of the weather, whether hot or cold, is extensively affected by
this trade current. As we have already suggested, the mere presence of the
sun in its summer solstice, or its absence in winter, is not an adequate
cause of all the sudden and various changes to which we are subject. The
state of the counter-trade, which is always over, or _within influential
distance of us_, and sometimes probably in contact with us--the nature of
the surface-winds which it is at any given time creating and attracting
around us, and the electric condition of the surface-atmosphere _induced_
by it, or by the immediate action of the earth's magnetism, produce those
sudden changes which mark our climate. When no intervening surface-winds
elevate it above us, and there is no storm or other condensation within
influential distance, it induces the gentle balmy S. W. wind of
spring--the cooling S. W. wind of summer--the peculiar Indian summer air
of autumn, or the comparatively moderate, although cold, open weather of
winter. If there be a partial tendency to condensation in it, the cumuli
form under the magnetic influence excited by the sunbeams from ten to
three o'clock in the day, and float gently away to the eastward,
disappearing before night-fall. If the disposition to condensation is
stronger, whether inherent or induced by an increased local activity of
terrestrial magnetism, these cumuli will increase toward night-fall, or
earlier, and terminate me showers; and if it is in a highly electrical
state, the still oppressive sultriness which precedes the tornado, and
that devastating scourge may appear. If this disposition to condensation
becomes extensive, cirri form and run into cirro-stratus, or they extend,
coalesce, and form stratus; the surface-wind will be attracted under them,
the thermometer fall in summer or rise in winter, and a storm begin.
Intense action and sudden cold may exist in and under this counter-trade
over the southern portion of the country, while all is calm, warm, and
balmy at the north. Heavy snow storms sometimes pass at the south when
there are none at the north, and a corresponding state of the weather
follows. If a large body of snow fall at the north, the winter is cold,
regular, and "old fashioned;" if little snow falls at the north and more
at the south, the winter at the north is open and broken. I have known the
ice make several inches thick at Baltimore and Washington, when none could
be obtained for the ice-houses on the Connecticut shore of Long Island
Sound. In short, although heat and cold are mainly dependent upon the
altitude of the sun, aided by the other arrangements we have alluded to,
yet the counter-trade, and the reciprocal action which takes place between
it and the earth, are most powerful agents, mitigating the rigors of
winter, bringing about the changes from cold to warm weather which the
sun is too far south to produce. And on the other hand, by this reciprocal
action, producing the electrical phenomena, the gusts, the tornadoes, the
hail storms, and the cool seasons of summer, and the period of intense
cold in winter.
_All our surface-winds, except the light, peculiar W. S. W. wind which is
felt where the counter-trade is in contact with the earth, and which is a
part of it, and perhaps the genuine N. W. wind which is very peculiar, are
incidents of the trade, and are due to its conditions and attractions._ We
have already said this was true of the easterly wind and scud of a
storm--it is alike true of all. The storm winds east of the Alleghanies
are usually, though not always, from the eastward. They are sometimes from
the southward, as they doubtless are still more frequently in the interior
of the continent.
There is occasionally a southerly afternoon wind, followed by short rains
in spring and fall, or a succession of showers in summer, which is rather
a precedent wind than a storm wind; blowing toward and under an advance
portion of the storm at the north, and hauling to the eastward when the
rain sets in, or to the westward when the showers reach us.
When there are no storms, or showers, or inducing electric action in the
counter-trade, within influential distance to disturb the surface
atmosphere, it is calm. If a storm approaches, or forms within inducing
distance, the surface atmosphere is _affected_ and _attracted toward the
storm_, from one or more points, and "blows," as we say, toward and under
it. It commences blowing first nearest the storm, and extends as the
storm travels, or becomes more intense and extends its inducing influence.
I have repeatedly noticed this in traveling on steamboats and railroads
running _toward_ or _from_, and in several instances _through_ a storm,
and telegraphic notices and other investigations prove it. The point from
which the surface atmosphere is attracted and blows, depends very much
upon the position of the storm in relation to bodies of water and the
point of observation, and its shape; and the force with which it may blow
will depend much upon its intensity.
Let us take an instance or two by way of illustration of all these points;
and as I have given instances of summer in the introduction, we will take
those of winter. It is January of an "old fashioned winter;" the snow is
about three feet deep in Canada, about one foot in Southern New York, and
a few inches in Philadelphia, and so extends west to the Alleghanies at
least. For several days the sky has been clear, the thermometer rising in
the day-time, in the vicinity of New York to about 25 deg. Fahrenheit, falling
at night to about 6 deg., with light airs from the N. W. during the middle and
latter part of the day; the counter-trade and the barometer both running
high; cold but pleasant, steady, winter weather. There is a warm
south-east rain and thaw coming, as one or more such almost invariably
occur in January. How coming? The sun is far south, and shines aslant, but
through a pure and windless atmosphere; he has tried for several days to
melt the snow from the roof; a few icicles are pendant from the eaves;
but the body of the snow is still there. How can a thaw come? not from the
sun, surely. No, indeed, not from the action of the sun directly, upon our
country, nor from the Atlantic or the Gulf Stream which is off our coast.
But a portion of the current of counter-trade is coming, heated by his
rays and the warm water in the South Atlantic, in an intense
magneto-electric state, capable of inducing an electro-thermal change in
the surface atmosphere which it approaches, and of being reciprocally
acted upon by the north polar terrestrial magnetism. It is now over
Northern Texas and Western Louisiana, it will be here day after tomorrow.
The day passes as the day previous had passed; the sleigh-bells jingle
merrily in the evening; the moon shines clear all night; the storm is
coming steadily on, but its influence has not reached us, and the morning
and midday are like those which preceded it. As nightfall approaches,
however, the thermometer does not fall as rapidly as on the day previous;
the sun shines dimly and through lines of whitish cirrus cloud extending
from the horizon at the west, appearing darker as the sun descends and
shines more _horizontally_ through them--perhaps mainly in the N. W.--and
which extend up and over toward the E. N. E. The air next the earth begins
to feel raw; it is changing, not from warm to cold, but _electrically_
from positive to negative; and dampening, from a tendency to condensation
by induction, as we shall see--the same condensation which in warm
weather may be seen on flagging stones, and walls, and vessels containing
cold water. The advance cirrus condensation of the storm is over us and
affecting us; the earth too is affecting the adjacent atmosphere by action
extended from beneath the storm. Still there is no wind, although sounds
seem to be heard a little more distinctly from the east, and so ends the
day. Evening comes, and the moon wades in a smooth bank of cirro-stratus
haze, with a very large circle around her; the cirrus bands of haze have
coalesced and formed a thin stratus. The storm is coming steadily on, its
condensation is seen to be thicker as it approaches, it is now raining
from one hundred to one hundred and fifty miles to the west, but we do not
know it.
That it is about to storm all believe, for all are conscious of a change.
The candle if extinguished will not relight as readily, if at all, on
being blown; there is a crackling almost too faint for snow in the fire;
the sun did not set clear; the old rheumatic joints complain, and the
venerable corns ache.
Morning comes, and the storm is on. The wind is blowing from the S. E.,
the scud are running rapidly from the same quarter to the N. W., the
thermometer continues rising, and it rains. The storm has reached us and
the thaw has commenced. Gradually, as the densest portion of the storm
cloud reaches us, it darkens; the scud are nearer the earth, and run with
more rapidity; the rain falls more heavily and continuously, and by the
middle of the day a thick fog has enveloped the earth; the wind is dying
away, and the trade itself, with its southern tendency to fog, has settled
near us; the barometer has fallen, the thermometer is up to fifty degrees,
the water is running down the hills, the snow is saturated with water and
is disappearing under the influence of the fog, the rain, and the warm
air. Evening comes; the south-east wind and the rain have ceased; the rain
clouds have passed off to the eastward; the fog has followed on and
disappeared; there is a light trade air from the S. W.; the moon shines
out, and a few patches of stratus, broken up into fragments and melting
away, are following on in the trade: the storm is past.
Hark! to the tones of Boreas as he bursts forth from the N. W., and
rushing, whistling, howling, dashes on between the trade and the earth,
following the storm. Now the barometer rises rapidly, the thermometer
falls, and in an incredibly short time all is congealed, and cold and
wintery as before. The cold N. W. wind has again interposed between the
trade and the earth; the trade is elevated a mile or more above it and is
entirely free from its influence and from condensation; the deep blue of a
sky "as pure as the spirit that made it" is over us, and steady winter
reigns again.
It is obvious that there was nothing in the action of the sun upon our
snow-clad country, to induce the thaw or the storm. It began, continued,
approached, and passed off to the N. E. in the counter-trade. The S. E.
wind which existed every where within its influence: in the interior
States, Missouri, Illinois, Indiana, Ohio, Michigan, and in Canada, as
well as upon the Atlantic coast, commencing in the former earlier than
upon the last, was the result of its induction and attraction. Of the N.
W. wind that followed we shall speak hereafter. If any one doubts whether
this be a true sketch let him examine the investigation of a storm
published by Professor Loomis, or observe for himself hereafter. If,
however, the storm of Professor Loomis is referred to, it should be
remembered that his notes show the occurrence of a slight distinct snow
storm at the N. W. stations one day in advance of the principal storm. The
latter appears first as rain at Fort Towson, on the nineteenth, moving
north and curving to the east--its center passing near St. Louis, and
south of Quebec, and the whole storm enlarging as it advanced.
Take another instance. Since the thaw it has not been quite as cold as
before; but the rain-soaked snow is hard and solid, the ground, where the
snow was blown or worn off, icy and slippery--the thermometer falls during
the night to about 12 deg., and rises to about 30 deg.; the sun makes no
impression upon the snow; the firmament is of the deepest blue, the
borealis at night vivid. "O, for a storm of some kind, to mitigate the
still severe cold;" for the thaw has made us more sensitive, and storm
winds do blow warm in their season. But patience, it will come. Another
day, or two, perhaps, pass: the sun rises as usual, the thermometer has
the same range still. "Long cold snap," we exclaim; "how long will it
last?"
A change is coming, but this time it will snow. About an hour or two after
sunrise the cirrus threads are discoverable again in the west, but now
they are most numerous in the S. W. As the day passes on they thicken and
advance toward the E. N. E., the sun begins to be obscured, the
thermometer rises, and it slowly "_moderates_." There is a snow storm
approaching from the S. W.
But the thermometer rises slowly; it must get up to 26 deg. or 28 deg. before it
can snow much. I have known in one instance, at Norwalk, a considerable
fall of snow, although much mingled with hail, when the thermometer stood
at 13 deg. above zero, and one, a moderate fall, some two inches, with it at
24 deg., but these were exceptions. The snow range of the thermometer on the
parallel of 41 deg. north latitude, and south of it, is from 26 deg. to 30 deg. above
0 deg.; when colder or warmer it may snow to whiten the ground, or perhaps
barely cover it, but usually rains or hails. We have seen that in the
polar regions, according to Dr. Kane, it is about zero, but the rise of
the thermometer there, previous to the snow, was about the same as here,
_i. e._, from 15 deg. to 25 deg.. This fact is instructive. Since the foregoing
was written, and on the 7th of February, 1855, a snow-storm of
considerable length set in, with the thermometer at 5 deg., and continued more
than twenty-four hours, the thermometer gradually rising. The snow was
very fine, like that described by Arctic voyagers as falling in extreme
cold weather.
As the dense and darker portions of the storm approach, and although the
sun is obscured, and the ground frozen, it continues to moderate, and at
evening, when the thermometer is up to 28 deg., and the dense portion of the
storm has reached us, gently and in calmness the snow begins to fall.
Perhaps a light air following the storm, or the presence of the trade near
the earth, at first inclines the snow-flakes to the eastward. This is
frequently so at the commencement of snow storms. Ere long, however, the
wind rises from the N. E., and the snow is driven against the windows,
rounded and hardened by the attrition of its flakes upon each other, in
their descent through the eddying and opposite currents. The next day we
rise to witness a heavy fall of snow, perhaps, and a continued driving N.
E. storm, in full blast; the snow whirling and settling in drifts under
the lee of every fence or building.
Can it be, you ask, that this driving wind is but an _incident_ of the
storm? the result of _attraction_, while the storm clouds are sailing
quietly and undisturbed on in the counter-trade above, directly over the
gale which is blowing below? It is even so. Nor has it "backed up," as it
is termed by those who have ascertained that it has commenced snowing
first, and cleared off first, at a point west of them. You saw, or might
have seen, the cirro-stratus cloud passing to the E. N. E. in the
afternoon, and until the snow-flakes filled the air, and the clouds became
invisible. You may still see that the wind will die away before the storm
breaks, and "come out" gently from the S. W., unless it should back into
the northward and westward, and in either event you may see the last of
the storm clouds, as you did see, or might have seen the first of them,
pass to the eastward. Toward night the wind dies away, and the storm
passes off abruptly, or the sky becomes clear in the N. W. Now you may see
the smooth stratus storm cloud, continuous, or breaking up into fragments
and passing off to the east, even at the edge which borders the clear sky
in the west or north-west, to be followed that evening or the next day, by
the north-west wind and its peculiar fair-weather scud.
I have given these as instances illustrating the manner in which rain and
snow storms originate the surface easterly winds in winter.
But it must not be supposed that they commence with precisely the same
appearances in every case in winter; much less in summer. There is very
great diversity in this respect, in different seasons, and in different
storms during the same season. A great many different and accurate
descriptions might be given, if time and space would permit, which all
would recognize as truthful. Very frequently in summer, and sometimes in
winter, the wind will set in from the eastward, and blow fresh toward a
storm, before the condensation in the trade, which forms the eastern and
approaching edge of the storm, has assumed the form of a distinct cloud.
Not unfrequently, when it is calm next the surface, a narrow stratum of
easterly wind, a half a mile or a mile above the earth, may be seen with a
continuous fog, condensing, but not in considerable patches like the
usual scud, running with great rapidity toward the storm. Such a stream of
fog blew with great rapidity for thirty-six hours toward the storm which
inundated Virginia and Pennsylvania, in 1852, and carried away the Potomac
bridge at Washington. Such a stream of fog was visible the evening before
the great flood of 1854, which inundated Connecticut, and curried away so
many railroad and other bridges. I have also seen such a stream of fog
running at about the same height, when it was calm at the surface, from
the S. W. toward a violent storm which formed over central New
England--and from the north toward a heavy storm passing south of us. Such
strata form, as far as I have been able to discover, the _middle current_
of storms which are accompanied with very heavy falls of rain. These
double currents are much more common than is supposed. East of the
Alleghanies, short and heavy rain storms, which commence north-east,
hauling to the south and lighting up about mid-day _after a very rainy
forenoon_, frequently have a S. E. or S. S. E. middle current of this
character, which involves the whole surface atmosphere when the storm has
nearly passed, and the N. E. wind dies away, and the wind seems to haul to
the S. S. E. and S.; so that it is rather the prevalence of a _different_
and _coexisting current_, than a hauling of the _same wind_, which marks
the period of lighting up in the south.
Sometimes the easterly wind will set in and blow a day or two before the
border of the storm reaches us. Sometimes the storm is passing, or will
pass, in its lateral southern extension, south of us, and the
condensation in the trade extends over us sufficiently dense to induce an
easterly current beneath it, but not dense enough to drop rain, and then
we have a dry north-easter. I can not, within the limits I have
prescribed, allude to all the peculiarities attending the induction and
attraction of an easterly wind, by the storm in the counter-trade. They
are readily noticeable by the attentive and discriminating observer, and
their existence and cause is all with which I have to do at present.
Winds from the north, or any point from N. N. E. to N. N. W., are
comparatively infrequent in the United States, east of the
Alleghanies--though it is otherwise in the vicinity of the great lakes.
Sometimes the wind "backs," as sailors term it, during a N. E. storm, from
the N. E. through the N. N. E., N., and N. N. W. to N. W. When this takes
place, it is toward the close of the storm. Occasionally, though very
rarely, it continues to storm after the wind has passed the point of N. N.
E., and until it gets N. W. I have known a few instances in the course of
thirty years, and but a few. They are exceptions--rare exceptions. When
the wind thus backs from the N. E. to the N. W. through the N., you may be
very certain that the body of the storm, or at least the point of greatest
intensity and greatest attraction, is at the time passing to the southward
of you. This is most commonly the course of the wind when the storm
extends far south and lasts several days, and does not extend north far,
or if so, with much intensity, beyond the point of observation. The
change of the wind is explained by the situation of the focus of intensity
and attraction, to the south of the observer, and its passage by on that
side.
Probably in locations further north and (as I think I have observed) south
of the lakes, it may be more frequent than upon the parallel of 44 deg. east
of the Alleghanies (which is as far north as I have observed), inasmuch as
the further north the locality, the more likely storms and other
disturbances in the counter-trade will be to pass to the southward of it.
Between the N. E. and S. E. the wind may blow from any point, before and
during storms, and in a clear day in the morning, as a light variable
breeze, or, after mid-day, toward approaching showers. I have known it
blow all day during a storm from due east; to change back and forth
between south-east and north-east, and to blow for hours from any
intermediate point--as different portions of the storm were of different
intensity, and exerted a more or less powerful inducing influence; and
doubtless this often takes place at sea. It depends upon the situation of
the focus of attraction of the storm, its shape relative to the particular
locality, and with reference to the atmosphere east of it, and peculiar
local magnetic action; or, as is sometimes the case in low latitudes, is
owing to the fact that the storm is made up of many imperfectly connected
showers, which have different force, and induce changeable and baffling
winds.
The inducing and attracting influence of the approaching storm is exerted
sooner, and with most force, upon the surface atmosphere, over bodies of
water like the ocean and the lakes. Thus, the wind will set from the
eastward toward an approaching storm out upon Long Island Sound, for hours
before it is felt upon either shore; and when all is calm in the evening
on land, and often before the moon forms a halo or circle in the milky
condensation of the approaching storm, or any sign of condensation is
visible, the breaking of the waves upon the shores may be heard. Doubtless
this may be observed on the shores of the Atlantic at other points.
This power of attracting the surface atmosphere from bodies of water like
the ocean and the great lakes, will account for two apparent anomalies,
mentioned by Mr. Blodget in a valuable and instructive article read to the
Scientific Convention, in 1853, regarding the annual fall of rain over the
United States.
First--the influence of mountains in extracting the water from the
atmospheric currents which pass over them, is well known and readily
explainable. Mr. Blodget, however, found that the source of our rains,
whatever it might be, when it reached the Alleghanies, was so far
exhausted of its moisture that those mountains extracted less from it than
fell to the westward, by some five to ten inches annually; and that the
fall of rain upon them was less than upon the Atlantic slope eastward of
them, to the ocean. This does not accord with observation elsewhere, but
is easily explained. As the storm approaches the ocean, it attracts in
under it the surface atmosphere of the ocean, loaded with vapor,
condensing in the form of fog and scud, as it becomes subject to the
increasing influence of the storm. Although the scud and fog would not of
itself make rain, it aids materially in increasing the quantity of that
which falls through it. The drops, by attraction and contact, enlarge
themselves as they pass through, in the same manner as a drop of water
will do in running down a pane of glass which is covered with moisture.
The small drop which starts from the upper portion of a fifteen-inch pane,
will sometimes more than double its size before it reaches the bottom. _It
is by this power of attracting the surface atmosphere, which contains the
moisture of evaporation, under it, and inducing condensation in it, that
the moisture of evaporation which rarely rises very far in the atmosphere
is made to fall again during storms and showers._ This attraction of a
moist atmosphere from the ocean accounts for the excess of rain on the
east of the Alleghanies, compared with its fall upon them. So the great
valley of the Mississippi is comparatively level, and less of its water
runs off than of that which falls upon the Alleghanies. There is,
therefore, more moisture of evaporation in the atmosphere of the former to
be thus precipitated and add to the annual supply of rain upon that
valley, and it exceeds that which falls upon the Alleghanies. Those
mountains, too, are elevated but about 1,500 feet above the table-lands at
their base, and exert little influence on the counter-trade. If they, were
6,000 or 8,000 feet high, a different state of things would exist.
Second--Mr. Blodget found the quantity of rain which fell in Iowa, and to
the south and west of the lake region, to be greater than fell over the
lake region itself. This is doubtless in part owing to the same cause. The
counter-trade, in a stormy state, attracts the surface atmosphere from the
lake region, with its evaporated moisture, before it arrives over it, and
therefore more rain falls S. W. of the lake region than upon it. This
power of attracting the surface wind of the ocean in under it, produces
the heavy gales which affect our coast, and which are rarely felt west of
the Alleghanies to any considerable degree; and a storm coming from the W.
S. W., extending a thousand miles or more from S. S. E. to N. N. W., may
have the wind set in violently at S. E. on the _southern coast first_, and
at later periods, successively, at points further north, and thus induce
the belief that the storm traveled from south to north.
Mr. Redfield finding that some of the gales which he investigated,
particularly that of September 3d, 1821, did not extend far inland, and
commenced at later periods regularly, at more northern points, concluded
that the gale traveled along the line of the coast to the northward. In
this, and in relation to the storm of 1821 (and perhaps some others), he
has been deceived. My recollections of that storm are accurate and
distinct. But I shall recur to this again when I come to speak of his
theory.
Toward storms, or belts of showers which would be storms if it were not
summer and the tropical tendency to showers active in the trade, which
pass mainly to the north of us, or commence north and pass over us,
condensing south while progressing east, the wind may commence blowing
before the body of the storm reaches us, from any point between south by
west and south east, particularly in the summer season and in the
afternoon. When the rain in a storm of this character sets in, in the
night, it will sometimes haul into the S. E., if the focus of attraction
be situated north of us, and so remain until just before the storm is to
break.
There are, however, a class of southerly summer winds which deserve more
particular notice. For two or three months in the year--say from the
middle of June to the 20th of August--storms on the eastern part of the
continent, except in wet seasons, are rare, and most of our rain is
derived from showers. During these periods belts of drought are frequent,
sometimes in one locality, and sometimes in another, extending with
considerable regularity from W. S. W. to E. N. E. in the course of the
counter-trade, while rain falls in frequent and almost daily showers to
the northward or southward of them. If the daily rains are at the north,
over the belt of drought, S. S. W. and S. W. by S. winds blow, sometimes
with cumuli or scud, during the middle of the day and afternoon, to
underlie the showery counter-trade on the north of the line of drought.
Thus, sometimes nearly every day for several days, the evaporated moisture
of the dry belt will be carried over to increase the store of those who
have a sufficient supply without. During the latter part of the afternoon
the clouds in the west may look very much like a gathering shower, but the
attractions of the counter-trade fifty or one or two hundred miles to the
north, will absorb them all, and at nightfall the wind will haul to the S.
W. on a line with the counter-trade, and die away.
If there be a drought on any given line of latitude, and frequent showers
or heavy rains at the south of it, although there may not be a like
surface-wind, with cumuli and fog, blowing from the north toward it, yet a
general, gentle set of the atmosphere, from the N. N. W., or N. W., or
other northerly point, toward the belt of rains, some distance above the
earth, will often be observable, with a barometer continually depressed,
and perhaps a cool atmosphere.
During set fair weather, when the attracting belt of rains is far north,
on the north shore of Long Island Sound, the wind, like a sea breeze, will
set in gently from about S. S. E. or S. by E. in the forenoon, blowing a
gentle breeze through the day, and hauling to W. S. W. on a line with the
trade at nightfall, and dying away. During a drought I have known this to
happen for seventeen successive days. It is obvious to an attentive
observer that this is the result of the influence of the sun in exciting
the magnetic influence of the earth, and producing a state of the trade
not unlike that which induces the formation of cumuli, and which attracts
the surface atmosphere from the Sound in over the land: for the _tendency
to cumulus condensation precedes the breeze_, and the breeze is often
wanting in the hottest days where no such tendency to the formation of
cumuli exists. The same is true of sea breezes elsewhere. They do not blow
in upon some of the hottest surfaces. Where they do exist, they do not
always blow, but are wanting during the hottest days; and careful
observers have identified their appearance with the formation of cumuli,
or other condensation, upon the hills inland. They are not, therefore, the
result of ascending currents of heated air.
The received theory regarding sea and land breezes is a mistaken one in
another respect. There is no such thing as a land wind corresponding in
force to, and the opposite of, the sea breeze--occasioned by the
comparative warmth of the ocean. These breezes blow mainly within the
trade-wind region. Of course they are either beneath the belt of rains or
the adjoining trades. They are said to be, and doubtless are, most active
and strongly marked on lines of coast, particularly the Malabar coast, and
where the trade-winds are drawing usually from them. In the day-time, when
the action of the sun increases the action of the magnetic currents upon
the land, or there are _elevations inland_ which approach the
counter-trade, and especially if it is elevated near the coast, as the
Malabar coast is by the Ghauts, the attraction of this atmosphere over it
_reverses the trade_, or inclines it in upon the land, and it blows in
obliquely or perpendicularly, according to the relative trending of the
coast and the direction of the surface-trade. Thus, where islands are
situated within the range of the trades, the latter will be _reversed_
during the day on the _leeward_ side, but continue to blow as land winds
during the night. So they are sometimes deflected in upon the land on the
sides, during the day, and in like manner return to their course in the
night. So, too, the north-east trades of Northern Africa, are occasionally
(though feebly where the coast is flat) deflected during the day-time, and
blow in as N. W. winds. Upon the southern coast of Africa the S. E. trade
is deflected, and blows in as a S. W. wind. Upon the south-western coast
of North America, the N. E. trades are deflected in like manner, and so
are the S. E. trades upon the western coast of South America. Where the
coast mountain ranges are very elevated, as upon the western coast of the
American continent, this attracting influence and consequent deflection
extends to a considerable distance seaward, and hence the westerly winds
of California, etc. It must be understood that we are now speaking of the
winds which blow within the range and during the existence of the
trade-winds or the presence of the dry belt--for the trades are not always
perceptible on the land. Captain Fitzroy thus describes the sea breezes of
the western coast of Peru, at 23 deg. south latitude. "The tops of the hills
on the coast of Peru are frequently covered with heavy clouds. The
prevailing winds are from S. S. E. to S. W., seldom stronger than a fresh
breeze, and often very slight. _Sometimes during the summer, for three or
four successive days, there is not a breath of wind, the sky is
beautifully clear, with a nearly vertical sun._ On the days that a sea
breeze sets in, it generally commences about ten in the morning, then
light and variable, but gradually increasing till one or two in the
afternoon. From that time a steady breeze prevails till near sunset, when
it begins to die away, and soon after the sun is down there is a calm.
About eight or nine in the evening _light winds_ come off the land, and
continue till sun-rise, when it again becomes calm until the sea breeze
sets in as before."
To illustrate this further, I take the following letter from Professor
Espy's Philosophy of Storms:
CLINTON HOTEL, N. Y., Dec. 20, 1839.
TO PROFESSOR ESPY,
DEAR SIR,--Understanding you are desirous of collecting curious
meteorological facts, I take the liberty of communicating to you what
I saw in the month of December, 1815, at the Island of Owhyhee. I lay
at that island in the Cavrico Bay,[3] in which Captain Cook was
killed, three weeks, and every day during that time, very soon after
the sea breeze set in, say about nine o'clock, a cloud began to form
round the lofty conical mountain in that island, in the form of a
ring, as the wooden horizon surrounds the terrestrial artificial
globe, and it soon began to rain in torrents, and continued through
the day. In the evening the sea breeze died away and the rain ceased,
and the cloud soon disappeared, and it remained entirely clear till
after the sea breeze set in next morning. The land breeze prevailed
during the night, and was so cool as to render fires pleasant to the
natives, which I observed they constantly kindled in the evening. I
was particularly struck with the phenomena of the cloud surrounding
the mountain, when none was ever seen in any other part of the sky,
and none then till after the sea breeze set in, in the morning, which
it did with wonderful regularity. The mountain stood in bold relief,
and its top could always be seen from where the ship lay, above the
cloud, even when it was the densest and blackest, with the lightning
flashing and the thunder rolling, as it did every day. I passed up
through the cloud once, and I know, therefore, how violently it
rains, especially at the lower side of the cloud. This rain never
extends beyond the base of the mountain;[4] and all round the horizon
there is eternally a cloudless sky. The dews, however, are very
heavy, and there seems to be no suffering for want of rain. That this
state of things continues all the year, I have no doubt, from what an
American, by name Sears, who had spent four years there, told me; he
had seen no change in regard to the rain.
CALEB WILLIAMS.
Providence, R. I.
Similar citations might be made to show that the sea breeze is induced by
the same cause which forms the clouds over the land--that it is frequently
wanting for three or four days under a vertical sun, and that the land
breeze blows gently and not with corresponding force where there is no
surface trade, or where it is deflected, not reversed.
A succession of showers passing across the country to the north, within
one hundred to one hundred and fifty miles, almost always produces a
southerly wind to the southward of them. There is more that is peculiar
about these belts of showers. Although they consist of large
highly-electrified cumuli, there is a strong tendency to cirro-stratus
condensation in the lower part of the trade over them; and it is that
condensation rather than the cumuli, which attracts the surface atmosphere
from the south. They would be storms, if the atmosphere had not a
summer-tropical tendency to showers. There is, too, a tendency in these
belts to extend to the south, and it is generally, as far as I have
observed, the extension southerly of those belts, by the formation of new
showers which terminate the "hot spells" or "heated terms" of mid-summer.
The very oppressive and fatal one of the summer of 1853, was, in
character, a type of all--although exceeding them in severity. The first
three or four days were calm, hot, and smoky--an appearance which attends
all similar periods more or less, refracting the red ray of the light, and
giving the sun a peculiar dry-weather, red appearance. (This smoky haze is
usually atmospheric, and occasionally seen even in March, although not
unfrequently fires in the woods fill the air with actual smoke, and very
much increase it, and when this is so, the odor of the smoke is often
perceptible.) Then we began to have a fresh south-west by south breeze in
the day-time, hauling to the south-west, and dying away at nightfall. The
next day, the tendency to condensation and consequent belt of showers
having extended further south and approached nearer to us, the S. S. W.
wind blew _fresher_ toward it, and _did not die away at nightfall_. During
the evening the reflection of the lightning playing upon the tops of the
thunder clouds, just visible at the north (heat-lightning, it is termed,
because supposed to be unaccompanied by thunder, but in reality lightning
reflected from clouds at too great a distance for the thunder to be
heard), and the continuance of the southerly wind after nightfall, gave
sure evidence of the coming showers the next day, and an end of the
excessive heat for that time. So ended both of those long-to-be-remembered
"heated terms" of 1853.
The same is probably true of the interior of the country every where.
Lieutenant Maury, in the course of his investigations, and in order to
ascertain the direction of the winds in the Mississippi valley during
rain, addressed a number of gentlemen, and received their replies, which
are published with his wind and current charts. Several answered, among
other things, that, "whenever the lightning appears to linger at the north
at eventide, rain almost invariably follows speedily; not so in the
south." Thus it frequently is with us. If, during a hot, dry time, of a
few days continuance, the lightning so lingers in the evening, and the
wind continues to blow _fresh_ from the southward _after nightfall_,
showers will generally follow within forty-eight hours, most commonly the
next day, and a cool N. N. W. or N. W. wind with a favorable change ensue.
Such, at least, has been the result of my observation for many years.
Indeed this seems to be the general law in summer in the Mississippi
valley, where the easterly winds are not so common as with us. To
illustrate this further, I copy from a recent work by T. Bassnett,
entitled the "Mechanical Theory of Storms," two short extracts, showing
the manner in which belts of showers extend southerly, while progressing
north-eastwardly, at Ottawa. The first occurred in August, 1853; the last,
December, 1852. The first was a belt of showers; the latter would have
been in August, but the lateness of the season changed its character
somewhat, though not entirely, to a more regular rain, especially toward
the close.
"AUGUST 6th.--Very fine and clear all day: wind from S. W.; a light
breeze; 8 P.M. frequent flashes of lightning in the northern sky; 10
P.M., a _low bank of dense clouds in north_, fringed with cirri,
visible during the flash of the lightning; 12 P.M., same continues.
"7th.--very fine and clear morning; wind S. W. moderate; noon, clouds
accumulating in the northern half of the sky; _wind fresher_, _S.
W._; 3 P.M., a clap of thunder over head, and black cumuli in west,
north, and east; 4 P.M., much thunder and scattered showers; six
miles west rained very heavily; 6 P.M., the heavy clouds passing over
to the south; 10 P.M., clear again in north.
"8th.--Clear all day; wind the same (S. W.); a hazy bank visible all
along on _southern horizon_.
"DECEMBER 21st, 1852.--Wind N. E., fine weather.
"22d.--Thick, hazy morning, wind east, much lighter in S. E. than in
N. W.; 8 A.M., a clear arch in S. E. getting more to south; noon,
_very black in W. N. W._; above, a broken layer of cirro-cumulus, the
sun visible sometimes through the waves; wind around to S. E., and
fresher; getting thicker all day; 10 P.M., _wind south, strong_;
thunder, lightning, and heavy rain all night, with strong squalls
from south.
"23d.--Wind S. W., moderate, drizzly day; 10 P.M., wind west, and
getting clearer."
It is obvious that the showers at the north passed east on the evening of
the 6th of August; that new showers, taking the same course, originated in
the north, but more southerly next day, with S. W. wind, and that they
passed east, and others formed successively further south, which passed
over the place of observation late in the afternoon, and that others
formed south and passed east during the night and next day, visible in a
bank on the southern horizon.
Later or earlier in the spring and autumn, these brisk afternoon
southerly winds continuing after nightfall, indicate moderate rains from a
rainy belt extending in a similar manner, without the cumuli and thunder
which attend those of mid-summer. I shall recur to this class of showers
and storms when we come to their classification.
Light surface winds from south-west to west are not often storm-winds, and
are usually those which the trade near the earth draws after it. Sometimes
the trade seems to draw the surface wind from the S. W. and W. S. W. with
considerable rapidity, and some scud a little distance above the earth.
When this is so, it will be found that a storm has passed to the north of
us, or a belt of rains is passing north, which may or may not have
sufficient southern extension to reach us. When there have been heavy
storms at the south in the spring, especially if of snow, the S. W. wind
which the trade draws after it, and which comes from the snowy or chilled
surface, is exceedingly "raw"--that is, damp and chilly, although not
thermometrically very cold. Probably every one has noticed these "_raw_"
S. W. winds of spring.
Usually, when storms and showers, which have not a southern lateral
extension, pass off, the trade is very near the earth, and a light S. W.
wind or calm follows for a longer or shorter period. Not unfrequently,
however, our N. E. storms terminate with a S. W. wind, shifting suddenly,
perhaps, just at the close of the storm, during what is sometimes called a
"clearing-off-shower," or, more frequently, dying gradually away as a N.
E. wind, and coming out gently from the S. W., following the retreating
cloud of the storm. In such cases it is said to "clear off warm."
With us the wind rarely blows from the west, except while slowly hauling
from some southerly point to the N. W. It is probably otherwise east of
the lakes and in some other localities to the north-west.
Occasionally, and most frequently in March, a W. to W. N. W. wind follows
storms, and blows with considerable severity, with large irregular,
squally masses of scud, and sometimes a gale. Such was the character of
the dry gale which crossed the country, particularly Northern New York, in
March, 1854, doing great damage. These westerly winds are always
accompanied by a continued depression of the barometer, and peculiar,
foggy, scuddy, condensation, and should be distinguished with care from
the regular and peculiar N. W. wind, as they may be, by the continued
depression of the barometer, and the character of the scud. They are
doubtless magnetic storms.
The remaining surface wind, the N. W., the genuine Boreas of our climate,
the invariable fair-weather wind, is one of great interest. It is unique
and peculiar. It is not the left-hand wind of a rotary gale, and has no
immediate connection with the storm. I have known it blow moderately,
fifteen successive days in winter; rising about ten A.M., and dying away
at nightfall. Occasionally, but very rarely indeed, a light wind exists
from the N. W. during a storm, owing probably to a focus of intensity in
relation to some surface the storm covers, like the focus which exhibits
itself as a clearing-off shower near the close of a storm; but the real
fair-weather Boreas is a different affair altogether. Let us observe with
care its peculiarities; they are instructive.
1st. It rarely blows with any considerable force beneath the trade while
there are storm clouds, or any considerable condensation in it. It does
not interfere with that reciprocal action which takes place between the
trade and the earth, during approaching or existing storms. I have
frequently seen it with its peculiar scud clouds in the N. W., waiting for
the storm condensation of the trade to pass by, that full of positive
electricity it might commence its sports; rushing and eddying along the
surface, licking up the warm, south polar, electric rain, which stood in
pools upon the ground, or rose in steamy vapor from the surface, and with
its cool breath dry up the muddy roads as no degree of heat can dry them.
The annexed figure (14) shows the appearance of the northern edge of a
stratus storm cloud, passing off E. N. E. at the close of the storm, which
was "_clearing off from the north-west_." It is from a daguerreotype view,
looking W. N. W., taken at eight o'clock in the morning, in the fall of
the year. Near the horizon maybe seen the N. W. scud, forming in the N. W.
wind, which is about to follow the retreating edge of the storm cloud.
Figure 15 is from a daguerreotype view, taken at eleven o'clock the same
day, when the storm cloud had passed off and its edge remained visible
only south of the zenith, and the north-east scud had risen up and covered
the northern half of the sky, and the wind was blowing a gale from that
quarter.
[Illustration: Fig. 14.]
Another view was taken about two P.M. of the same day, when the scud had a
very dark, gloomy appearance--as _dark_ and _gloomy_ as those of a Mexican
norther--too dark to represent by a cut.
Not unfrequently in a moist summer season, after a day of showers or rain,
which have had an extending formation or lateral extension from north to
south, it will commence blowing in the morning, and encourage the
hay-maker with the hope of fine weather. But often before noon, the milky
stratus condensation above with cumuli below, will appear in the trade;
the N. W. wind die away and variable airs from the east or south appear,
to be followed toward night by an enlargement of the cumuli and showers.
It rarely, if ever, blows fresh till the storm condensation of the trade
has passed; or continues to blow after that condensation reappears. When
it commences blowing after a storm, and the northern edge of the storm is
not over us, we may frequently see the latter low down in the S. E.
passing eastward.
[Illustration: Fig. 15. NORTH VIEW.]
2d. Its scud are peculiar. Every one, probably, has noticed them. They are
distinct, more or less disconnected, irregular, with every form between
those of the easterly scud, cumulus, and stratus, according to the season.
If large, with _dark under surfaces_; forming _rapidly_ and as _rapidly
dissolving_; rarely dropping any rain, sometimes dropping a flurry of
snow, in November or March, oftener than at any other period; sailing away
to the S. E., and casting a traveling shadow as they pass on over the
surface of the earth. Their electricity, particularly when white, is
probably always positive, as that of all whitish clouds is supposed to be.
3d. _It is emphatically a surface wind._ The incident storm winds, the N.
E. and S. E., frequently _commence blowing_ under the storm, toward its
point of greatest intensity, _up near the line of cirro-stratus
condensation_, evidenced by the running scud; or blow there with most
rapidity, and so continue for hours before the whole surface atmosphere
from thence to the earth becomes involved in the movement; and sometimes
without being felt below at all. Not so with the N. W. wind; it _begins at
the surface_ and blows there with more rapidity than above; it seems to be
attracted by the earth; it interposes between the earth and the trade,
wedging the trade up and occupying its place. It blows under at all
seasons of the year, but most readily and strongly from a surface of snow
whose electricity is always positive. Hence it blows most strongly and
_continuously_ when snow has fallen at the north, and prevails during
winter very much in proportion to the extent and continuance of the
covering of snow which invests the earth in that direction. It follows
after storms, and particularly warm rains, during the autumn, winter, and
spring months, which have a lateral southern extension. Whether it is
increased by the snow from the surface from which it blows, or is caused
by the same magnetic action which causes the great fall of snow, is a
question we shall consider hereafter.
4th. It does not connect or mingle with the trade current in any way, or
change or divert the course of that current; but interposes between it and
the earth, elevating the trade in proportion to its own volume, above the
influences of the earth (when the trade becomes free from condensation,
and singularly, clear); and raising _proportionately_ the barometer. An
experienced observer can frequently estimate, with considerable accuracy,
the rise of the barometer, by measuring with his eye, (when the clouds
will enable him to do so,) the depth of this interposed N. W. current. The
barometer rarely rises after a storm, for twenty-four or forty-eight hours
if the wind continues at any point from S. W. to W. N. W., but always
rapidly as soon as the genuine N. W. current with any considerable depth
interposes and elevates the trade.
It will be obvious to every one, I think, certainly, if they will
hereafter study the subject and observe for themselves, that the N. W.
wind does not blow away the storm; and that it follows after it, blowing
over the surface which is uncovered by the storm; rarely, if ever, with
any force when the body of the storm passed south of us; and that it is a
purely surface wind, seemingly attracted by the peculiar magneto-electric
state in which the surface of the earth is left, compared with a snow-clad
surface to the north, by a recent storm, or that peculiar state of the
trade which is left by the action of the storm. It seems to follow that
magnetic wave which, passing from north to south, acts in its course upon
the counter-trade, producing the storm, or belt of showers, and giving
them their southern lateral extension, and will well repay future
telegraphic investigation. Its electricity is intensely positive--that of
the earth by the action of the storm as intensely negative.
5th. This N. W. wind occurs in all parts of the northern hemisphere, so
far as we have data to determine, and its corresponding wind from the S.
W. occurs in the southern hemisphere. It is identical with a class of the
northers of the Gulf of Mexico, as a brief analysis of the character of
the latter will show.
1st. The fall and winter _norther_ is a dry wind without rain or falling
weather--so is our N. W. wind.
2d. It is preceded by a falling barometer; S. E. scud and rain at the
point where it blows, or to the eastward of it. So is ours when it blows a
gale in the fall and spring months, which bear the nearest resemblance in
climatic character to the periods when the northers blow. With this
distinction, however, that our precedent rains either pass over us or to
the southward, the direction of storms being E. N. E.; their precedent
storms passing over or to the eastward of them as they move more to the
northward.
3d. It is often preceded by a copious dew; so is ours--such dews often
following light fall rains in our climate, and preceding N. W. wind.
4th. The most peculiar characteristic, however, is that the barometer
rises rapidly and invariably while the norther prevails, and very much in
proportion to its violence. The same is true of our genuine N. W. wind,
and is not true _of any other wind_ on this continent which I have
observed or read of.
5th. While they are thus alike in these respects, they are unlike in no
respect.
Mr. Redfield has traced them in _supposed_ connection with storms which
continue from that vicinity across the United States to the E. N. E., and
endeavored to connect them with those storms, as the left-hand winds of a
rotary gale. Obviously, I think, they are identical with our N. W. winds
which also _follow_, indeed, but _are distinct from the storms_.
There are a class of northers in the Gulf of Mexico--the "Nortes del Muero
Colorado"--sometimes occurring in the summer months, beginning at N. E.,
veering about and settling at N. N. W., and as they decline hauling round
by the west to the southward. These winds correspond precisely with the
hurricane winds of the West Indies, and are doubtless the incident winds
of a storm traveling thence to the N. N. W. precisely as our N. E. or E.
N. E gales are incident storm winds to the N. E. storms of our latitude.
In this connection we will look at the peculiarities of a West India
hurricane.
"It is not a little remarkable," says Mr. Espy, speaking of the storms and
hurricanes of the West Indies, "that all these storms, and _all others
which have been traced to the West Indies_, traveled N. W. almost at right
angles to the direction of the trade-wind in those latitudes, but very
nearly, if not exactly, in the direction of an upper current of the air
known to exist there toward the N. W." Substantially the same facts have
been repeated by Mr. Redfield, and demonstrated by his able
investigations, both there and in the Eastern Pacific, and are confirmed
by the observations of Edwards, Lawson, and others, while residents there.
It is a matter of surprise that gentlemen like Messrs. Redfield and Espy,
who have certainly displayed great ability in the investigations of
meteorological phenomena, should fail to recognize a more intimate
relation between this upper current and the storms they were
investigating, and to detect the general laws which govern both. The
storms and hurricanes of the West Indies are comparatively of small
diameter, and have little advance condensation. When they pass on to the
south-western portion of North America and curve to the N. E., as they
frequently do, they enlarge in front and at the sides, and their advance
condensation, which is not dense enough to drop rain, extends in some
cases from one to three hundred miles; and the storm itself, by the time
it reaches the Alleghanies, may extend one thousand to fifteen hundred
miles, and perhaps in certain magnetic states of the surface, and
occasionally, may cover the entire portion of the continent, from north to
south. Such, probably, was very nearly the extension of the storm
investigated by Professor Loomis. In the West Indies, however, at the
commencement, they vary from twenty to one hundred miles, or possibly
more, in width.
First, they are preceded by a hot, sultry and oppressive atmosphere--_as
are electric storms every where_--a peculiar electric state of the earth
and adjacent air.