IN SUMMER.
Fig. 11.
IN WINTER.
Such are themainphenomena,at the surface, in the trade-wind region. Ascending a step higher in the atmosphere, we find, above the surface-trades, a counter-trade, running, not in the opposite direction, but at right angles, or nearly so. The counter-trade which issues from the northern side of the rainy belt, running to the N. W. or W. N. W., and the counter trade which issues from the southern side, running to the S. W. or W. S. W., varying, as the trades do in direction in different localities. These counter-trades are continuations of the surface trades, which, ascending in their course, have threaded their way through the opposite trade in the rainy belt, and are continuing on at the same angle, and in the same direction at which they blew upon the surface, and in obedience to the same law. This is apparent from several considerations.
1st. They issue at the same angle, and over the top of the surface trades. In the West Indies and elsewhere, this has been ascertained and proved by the course of the storms, and the rotation of their surface winds, and observation.
2d. We can not suppose the N. E. trade to be reflected, and turn back over itself at a right angle. That would be impossible, even if there were a wall of solid material there for it to blow against. Air is a peculiar fluid, and it stratifies with astonishing ease. He who supposes that a current of air put in motion can be turned aside by another current, or by the atmosphere at rest, or can be made to mingle, is mistaken. It will stratify, and force itself onward through the adjacent and opposing atmosphere, and in a right line. I have observed some remarkable instances of this character.
3d. The cause which operates to produce the surface trades, still operates upon the current to carry it over into the other hemisphere; a counter-trade, as we shall see. It is impossible, therefore, to believe that the surface-trades as they arrive at the belt of rains and calms, turn at a right angle, or at any angle, and return: and impossible to doubt that they pass through each other in this belt, and out at the opposite side, as upper currents, at the same angle at which they entered. Of course the N. E. trade of the Atlantic becomes the N. E. counter-trade of South America, carrying their storms in a S. W. direction, and the S. E. trade of the Atlantic the S. E. counter-trade of the West Indies, carryingall their storms in a N. W. direction; and what is true of them is true of the trade windsevery where, all over the globe, over the land and over the sea.
Doubtless here some one will say, our upper current is a S. W. current. True, the S. E. trade which enters the belt of rains, and issues out on the north, a S. E. upper current or counter-trade, keeps that course until it arrives at the northern limit of the surface trade, when, inobedience to another law, which we shall notice, it graduallydecends near the surface, curves to the eastward, and becomesthe S. W. current which passes over us. And so we have the S. E. trade-wind of the South Atlantic, with its moisture, warmth, electricity, and polarity, over, and perhaps sometimes around us, dropping the electric rain which makes glad our fields; giving us, when not prevented by other conditions, the balmy air of spring, the Indian summer of autumn, and the mild mitigating changes of winter; and thus,our rivers, which run into the sea, return to us again.
But let us go back to the trade-wind region—the region of regularity and uniformity—and examine somewhat more attentively its features, that we may more fully understand the character of this counter-trade.
Here are 60° at least of the 180° of the earth’s surface, and at its largest diameter, covered in the course of the year, and of their travels, by the trade-winds at the surface, the counter-trades above, and the belt of rains and comparative calms, formed by the action of the opposite trades, as they threadtheir way through each other, to assume the relation of counter-trades. Truly the magnitude, simplicity, and regularity of this machinery are most wonderful.
There are, however, someapparentanomalies which deserve attention. Here are most distinctly marked therainyanddry seasons, existing side by side. Here are therainless portionsof the earth, already but briefly alluded to; here themonsoons, and another peculiarity,viz.: thegathering of the counter-tradesupon the western sides of the two great oceans, into twoaerial currents of greater volume,analogoussomewhat to the twogulf streamsof those oceans. Let us examine these anomalies.
The rainy and dry seasons depend, as we have seen, upon the transit north and south of the rainy belt, or belt of comparative calms. Wherever this belt may happen on any given day to be situated, each side of it the trades prevail, it is dry, the earth is parched, and vegetation withers. These changes are graphically described by Humboldt in his “Views of Nature,” as they occur on the northern portions of South America, as follows: “When, beneath the vertical rays of the bright and cloudless sun of the tropics, the parched sward crumbles into dust, then the indurated soil cracks and bursts, as if rent asunder by some mighty earthquake. The hot and dusty earth forms a cloudy vail, which shrouds the heavens from view, and increases the stifling oppression of the atmosphere; while the east wind (i. e.trade-wind), when it blows over the long heated soil, instead of cooling, adds to the burning glow.
“Gradually, too, the pools of water, which had been protected from evaporation by the now seared foliage of the fan-palm, disappear. As in the icy north animals become torpid from cold, so here the crocodile and the boa-constrictor lie wrapped in unbroken sleep, deeply buried in the dried soil. Every where the drought announces death, yet every where the thirsty wanderer is deluded by the phantom of a moving, undulating, watery surface, created by the deceptive play of the reflected rays of light (the mirage). A narrow stratum separates the ground from the distant palm-trees, which seem to hover aloft, owing to the contact of currents of air having different degrees of heat, and therefore of density. Shrouded in dark clouds of dust, and tortured by hunger and burning thirst, oxen and horses scour the plain, the one belowing dismally, the other with outstretched necks snuffing the wind, in the endeavor to detect, by the moisture in the air, the vicinity of some pool of water not yet wholly evaporated.
“Even if the burning heat of day be succeeded by the cool freshness of the night, here always of equal length, the wearied ox and horse enjoy no repose. Huge bats now attack the animals during sleep, and vampyre-like suck their blood; or, fastening on their backs, raise festering wounds, in which mosquitos, hippobosces, and a host of other stinging insects, burrow and nestle. Such is the miserable existence of these poor animals, when the heat of the sun has absorbed the waters from the surface of the earth.
“When, after a long drought, the genial season of rain arrives, the scene suddenly changes. The deep azure of the hitherto cloudless sky assumes a lighter hue. Scarcely can the dark space in the constellation of the Southern Cross be distinguished at night. The mild phosphorescence of the Magellanic clouds fades away. Even the vertical stars of the constellations Aquila and Ophiuchus, shine with a flickering and less planetary light. Like some distant mountain, a single cloud is seen rising perpendicularly on the southern horizon. Misty vapors collect and gradually overspread the heavens, while distant thunder proclaims the approach of the vivifying rain. Scarcely is the surface of the earth moistened, before the teeming steppe becomes covered with Killingiæ, with the many-panicled Paspalum, and a variety of grasses. Excited by the power of light, the herbaceous Mimosa unfolds its dormant, drooping leaves, hailing, as it were, the rising sun in chorus with the matin song of the birds, and the opening flowers of aquatics. Horses and oxen, buoyant with life and enjoyment, roam over and crop the plains. The luxuriant grass hides the beautiful and spotted jaguar, who, lurking in safe concealment, and carefully measuring the extent of the leap, darts, like the Asiatic tiger, with a cat-like bound on his passing prey.”
Such is Humboldt’s description of the dry season on the Orinoco, and the return of the belt of rains from the south.
Again, within this trade-wind region are therainless countries. These are portions of the earth which the equatorial rainy belt does not ascend far enough north in summer to cover, nor does the southern edge of the extra-tropical regular rains descend, in winter, far enough south to cover them, and where, of course, rain seldom, if ever, falls. Such are the central parts of the Desert of Sahara, Egypt, Arabia, portions of Affghanistan, Beloochistan, and the western parts of Hindoostan, to the north of the inter-tropical belt, and a similar state of things exists south of the equator in parts of South America, Africa, and New Holland, although upon a comparatively small surface.
Again, another anomaly is the gathering of the trade winds into greater volumes, on the westerly side of the great oceans, and the consequent carrying of the equatorial rainy belt up to the region of extra-tropical rains, on the eastern side of the great continents of Asia and North America, and the peculiar liability of these aerial gulfs to hurricanes and typhoons. Such an aerial gulf gathers over the Caribbean Sea, and the West Indies. Passing across the Gulf of Mexico, it enters over Texas, and Louisiana, and the other southern states; its western edge passing north in autumn and winter, on the eastern side of the highlands of Western Texas, New Mexico, and the Great Desert; curving, as all counter-trades do, to the eastward as soon as it passes the limit of the N. E. trades, and spreading out over our favored country, leaving the evidence of its pathway in the greater quantities of rain, which fall annually uponits surface. This gathering deprives a portion of the Atlantic, north of the tropics, of its share of the counter trade, and there, as every where, where the volume of counter-trade is small, storms and gales are infrequent, and of less force, and comparative calms prevail. That portion of the Atlantic has long been known as “the horse latitudes,” a name given to it by our Yankee sailors, because, there, in former times, the old-fashioned, low-decked, flat-bottomed, horse-carrying craft of New England, bound for the West Indies, often floundered about in the calms and baffling winds, until their animals perished for want of water, and were thrown overboard. Lieutenant Maury, in his most praiseworthy and exceedingly useful investigation of “The Winds and Currents of the Ocean,” has defined the situation of these calms and baffling winds at different seasons—for they move up and down, of course, with the motion of the whole machinery—and enabled navigators to avoid them, by runningeastbefore they attempt to makesouthing; and very materially shortened the voyages to the equator.
A like gathering, in volume, of the S. E. trade, on the western side of the Pacific, enters over Asia, and covers China and Malaysia, extending, in its western course, nearly as far as the western edge of Hindoostan. In this concentrated volume of counter-trade, and owing to its concentrated action, form and float the typhoons of the China Sea, and of the Bay of Bengal; and to this anomalous aerial gulf stream, the S. E. portions of Asia, from the western desertof Hindoostan, to the eastern portion of China, north of the rainy belt, owe their great supply of moisture and fertility, and their peculiar climate. The western line of this volume of counter-trade is marked by the eastern portion of the rainless region of Beloochistan, and the north-western deserts of India, as the western edge of our concentrated volume of counter-trade, is marked by the arid plains of northern Mexico, western Texas, and New Mexico. On the south of the equatorial rainy belt, there is no corresponding aerial gulf of equal volume, as there is no corresponding gulf stream of equal magnitude. On the western side of the Indian Ocean we find a gathering of the N. E. trades from the Bay of Bengal and the Indian Ocean, in which form and travel the hurricanes which prevail—traveling to the southward and westward—about the Isle of France or Mauritius; and the lagullus oceanic current, which runs down to the S. W. toward the Cape of Good Hope. But the extension of South America to the eastward, under, or just south of the N. E. trades, does not permit the formation of such a concentrated volume on the western side of the Atlantic, nor is the strength or regularity of the N. E. trades, on that ocean, equal to those of the S. E.
Nor is the magnetic intensity on the eastern and middle portions of the Pacific, sufficient to produce such a concentration, in large volume, there. The trades over that ocean, therefore, curve without concentration, except a partial one, over the western groups of Polynesia, which the Asiatic line ofmagnetic intensity approaches and where hurricanes are sometimes found, until we arrive near the eastern line of magnetic intensity, on the eastern side of Asia. We shall, hereafter, have occasion to follow the anomalous concentrated volumes of the S. E. counter-trade, of the northern tropic, on the western side of the great oceans, in explanation of some of the phenomena which we find north of the trade-wind region. Suffice it here to add, that if it were not for the concentration of these counter-trades, on the western side of the great oceans, the rainless region between the parallels of 20° and 30° would encircle the earth; and China and the Eastern United States would have a distinctly marked rainy and dry season, as have California, the Barbary States, Syria, Persia, and other countries which lie north of the rainless region, within the summer range of the N. E. trades, but also within the winter descending range of the belt of extra-tropical rains.
Another anomaly which we find in the trade-wind region, is the monsoon. There are several of them, but they are found, in the greatest strength and regularity, in the Indian Ocean. Another, defined by the investigations of Maury, is found on the west coast of Africa, extending out over the Atlantic. Another prevails on the western coast of South and Central America. The etesian winds of the Mediterranean are but the N. E. trades, whose northern limit is carried up in summer, by the transit of the connected machinery, to the north, over that sea. The N. E. and S. E. monsoons, so called, of the Indian Ocean,are but the regular trades, blowing when the belt of rains is absent, as they do all over the globe. The N. W. monsoon, south of the equator, in the vicinity of New Holland; the S. W. monsoon which blows from the Arabian Sea, in upon Hindoostan; the S. W. monsoon of the Atlantic, south of the Cape De Verde Islands; and the variable west monsoon winds of the west coast of Southern and Central America, and Southern Mexico (known under several different names, but chiefly by that of Tapayaguas), are all that deserve attention as such.
At first sight they appear to be anomalies, but the facts declare their character with perfect certainty. First, they are not continuous, like the trades, butprevailingwinds, and arestorm winds;they always blow toward a region,or portion of the ocean,covered at the time by clouds and falling weather.
Second, they do not blow upon, or toward, heated surfaces of land or water—i. e., toward the dry and parched surfaces, where the dry season prevails, or from adjoining cold waters on to warm surfaces, but toward the land or watersituated under the rainy belt. They are therefore incident storm winds, (as our easterly winds are incident storm winds) of the rain clouds of the tropics. They blow in upon the land, under the belt of rains, while that belt with its daily cloud, and inducing electric action, is over it, and follow that belt in its transit north and south. They blow from the warm south polar current of the Atlantic, which flows N. W. from the coast of Africa, toward the inshore north polar current, which isthere flowing south, but under the belt of rains. In the Indian Ocean they blow from the center of that ocean, and the Arabian Sea, toward the belt which hangs over Hindoostan, from the S. W.; and when the rainy belt travels south they still blow toward, and under it, from the Indian Ocean, but of course from the N. W. The heated character of the waters of the Indian Ocean and Arabian Sea, which receive no polar currents, but heated waters from the Persian Gulf, and from rivers which flow into the Bay of Bengal over the heated plains of a tropical country, explain this. So, too, the monsoon of the Atlantic Ocean, does not blow north of the Cape De Verde Islands,—where the heated surface of Sahara, burning with the rays of a vertical sun, has a temperature sometimes ranging from one hundred and forty to one hundred and sixty degrees—but remains under the rainy belt, drawn from the heated waters which flow up from the South Atlantic, and travels north as the rainy belt travels north in summer, and south to the Gulf of Guinea, as that travels south in winter. The same is true of the Pacific monsoon, the Tapayaguas, the least marked of all, which blows in during the rainy season upon the west coast of Southern Mexico, and of Southern and Central America. They are all incident rain or storm winds, blowing in upon the land, or on to a colder surface of different polarity,during the rainy season; and if it were possible to catch one of our north-easters, in its passage over our country to the eastward, and anchor it to the Alleghanies, “paying out” so to have it reach in part overthe Atlantic, and keep it there in operation six months, we should have a continual easterly wind under it; amonsoonmore strongly marked than the monsoons of the Indian, or Atlantic Oceans.The received theory in relation to them is a fallacy.
Recapitulating, then, all the phenomena, we have,—Surface-trades, blowing toward the center, passing through each other, and continuing on as upper or counter-trades; abelt of rains, with calms near the center, formed by the trades where they meet and pass through each other, which travels with them north and south following the sun;two belts of drought, following the belt of rains and the trades, and followed by theextra-tropical line of rains, as it travels with the trades and the rainy belt, leaving a part of the earth which the equatorial rainy belt does not travel far enough north, nor the extra-tropical line of rains far enough south to cover, and which is consequently arainless region;the monsoons, which are but incidents of the rainy belt, and thegathered volumesof counter-trade, on the west of the two great oceans, which usurp the place of the N. E. trades, carrying the rainy belt up to the region of extra-tropical rain, and preventing the rainless region from encircling the earth.
Uponwhat causedo these great central phenomena, so vast, so regular, so wonderful, depend? What is themotive powerof this connected atmospheric machinery, whose action and influence extend over the entire globe?
“Heat, heat,” say the text books, the Professors,the votaries of meteorology. “All these phenomena are owing to the heat of the sun. It heats the ocean and the earth—the air is thereby heated and rises, the cold air rushes in from below, then the ascended current rolls off each way at the top toward the pole, acquiring a westerly motion from the rotation of the earth, slipping away from under it, and a different,viz.: an easterly motion, after reaching the latitude of 30°, from thesame rotation; and all the winds and disturbances of the atmosphere are produced in the same way. They are produced by the action of heated surfaces upon the adjacent atmosphere.”
This is the great theory of meteorologists, by which they attempt to account for the various atmospherical disturbances, of both tropical and extra-tropical regions.
The whole theory is a fallacy—it will not stand the test of a careful examination. The bases of the theory, which are assumed to be facts, are not so. The agent has not the power claimed for it. A heated surface, alone, never caused any considerable ascending current, or if it did, never produced a mile of wind. I repeat it, the theory and all incidental ones—the thousand explanatory and modifying theories, and hypotheses—the whole system—is without foundation in fact, and will not bear a critical examination.
Let us see if this language is stronger than the facts will warrant.
The theory assumes that both the land and water, under this central belt, where the air issupposed to be rising arematerially hotterthan the land and ocean are oneither side of it. Now, how much hotter are the air and the land under the belt of rains and calms, upon Hindoostan, or Africa, or South America, where the former is supposed to be acquiring heat and expansion so rapidly, and to be ascending, than under, and in the dry belts on either side? None; it is cooler by the thermometer—much cooler.
The central belt of rains in midsummer over Africa, extends up as far as 17° north latitude, and perhaps further. North of this line over the whole surface of the desert, the Barbary States, a part of the Mediterranean, and some portion of Italy, the dry season extends, and from the entire surface the N. E. trade blow into the central belt.[1]Over the desert they all pass. Now this desert is a sea of sand, under a vertical sun, intensely heated, blistering the skin with which it comes in contact, and often acquiring a temperature of 150° to 160° of Fahrenheit. Under the central belt of rains neither the earth nor air exceed the temperature of 84°. And yet the hot air of the desert does not ascend, but blows into this cooler central belt; and when it is felt as it blows off the western coast by the mariner, or even in Guinea, when the belt of rains has gone south in winter, as it often is as theharmattan, it is suffocating and intolerable. There, then, not only is it untrue, that the land and the air over it under the rainy belt are hotter, but it is true that intenselyheated air blows horizontally from the Desert of Sahara. Nay, as it will appear in the sequel, this hottest of all surfaces not only can not have a vortex, but it can not induce a monsoon, and scarcely a sea breeze. The same is true in a great degree of the surface, and the air over it, on either side of the supposed vortex of the rainy belt upon South America. See the description of Humboldt, already given, where the thermometer stood as high as 115° of Fahrenheit in the shade, while the N. E. winds, the regular trades, were blowing over the land. And it is equally true of Arabia, and indeed of every portion of the earth. There is not a spot upon the globe where the land and the air are coolerby the sideof the central belt of rains, thanunder it.And the opposite is true every where upon the land.
How much hotter is the ocean and air under this supposed vortex? But little hotter than they are on the side where the sun is not vertical,and none on the other. Let us be a little more particular. The temperature of the Atlantic under the belt of rains in our winter, and on the south of the belt at the latitude of 3° south, and down to 9° or more south, is 82°. The air may range a degree, or possibly two, higher than the water at either point. On the north this difference is from nothing at the meeting of the trades and belt of rains, to about 4° at their northern limit. This is tootriflingto be worth one moment’s consideration. It is less, far less than the difference between the water and air of the Gulf Stream which runs along our coast, and the adjoiningwaters and air over them. While on the south side of the belt of rains thedifference is actually against the theory—and the same state of things is reversed in summer, when the sun is vertical at the north.
From the log of an intelligent shipmaster, found in the wind and current charts of Lieutenant Maury, I abridge the following, which will illustrate this. Captain Young in February, found the N. E. trades at about 17° north latitude, with the water at 75° and air at 76°, trade-wind N. E.
Here the air was seven degrees colder at the extreme limit of the N. E. trades than in thecenterof the belt of rains, as it is, usually, in mid-winter, but not in summer. On the other hand,after he left the region of calms and rains, where the water and air stood with almost entire uniformity at 82°, on the 3d of March, and for three days thereafter, during which he was in the S. E. trades with fairweather, the water was the same as under the supposed vortex,viz., 82°,and the air rose to 83° and 84°!This is demonstration.
I also take from a letter of Lieutenant Walsh to Lieutenant Maury, relative to the cruise of the “Taney” the following, showing the warmth of the Gulf Stream compared with the adjacent ocean.
“We first crossed the Gulf Stream on the 31st of October; we struck it in latitude 37° 22′, longitude 71° 26′ as indicated by the temperature of the water, which was as follows:8A.M.water atsurface66°9"""73°10"""76°11"""77°77° was the highest temperature found in crossing at this time.Re-crossing it in May, in latitude 35° 30′, longitude 72° 35′, he found the water as follows:8A.M.water atsurface71° 8′9"""73°10"""75° 5′11"""78° 5′12M.""78° 5′79° being the highest temperature found.”
“We first crossed the Gulf Stream on the 31st of October; we struck it in latitude 37° 22′, longitude 71° 26′ as indicated by the temperature of the water, which was as follows:
77° was the highest temperature found in crossing at this time.
Re-crossing it in May, in latitude 35° 30′, longitude 72° 35′, he found the water as follows:
79° being the highest temperature found.”
The average difference between the temperature of the water of the Gulf Stream and the adjoining ocean, at the line of division, is about ten degrees, increasing to more than twenty on approaching the coast, and within one hundred miles—a far greater difference than is ever found on the winter side of the inter-tropical rainy belt.
It is not only not so, then, that the surface of theocean is materially warmer under the belt of rains than the adjoining surface under the trades, especially on the summer side, but if it were so, the trades would not be created thereby, any more than upon the Gulf Stream. And the opposite is true of the land where the line of calms, and rains, and drought meet, all around the globe. The fact assumed is therefore untrue. The hottest surfaces, even at the rainless portion, where there is no vortex, no storm, and no wind but the continual uniform N. E. horizontal trade-wind,nevercreated, by reason of the heat alone, a mile of wind, a storm or shower.
But, again, the belt of calms, where the air is supposed to rise and create a suction which draws the trades on either side a distance of from one thousand to two thousand miles, an average of three thousand miles in all, at least, is not itself, on an average, over five hundred miles in breadth from north to south. What a wonder of meteorology is here!
With a breadth of five hundred miles, the rising of the atmosphere is supposed to be so rapid and of such immense volume that it draws the surface atmosphere, one thousand to fifteen hundred miles on one side and two thousand on the other, with a uniform steady velocity of twenty miles per hour. Is this vast suction found by the unlucky mariner who may be drawn within the vortex?Not at all.He finds no rapid suction there, buthorizontal currents, not steady, indeed, like the trades, and sometimes calmsat the center, but still thecurrents are there, and,exceptnear the center, there as squalls, showers, and baffling winds and as monsoons.
Again, is there at the mouth of this vortex, or as you approach it, an increased rapidity in the trade corresponding to the magnitude of its influence? Does the trade become a hurricane as it approaches the spot where it is to supply the place of that which has suddenly “expanded by heat, and been forced to rise, boil over, and run off at the top in turn?” Not at all. It blows gently, even up to the very line of the rainy belt, and becomes squally and baffling, falls gradually calm near the center, or changes to a monsoon.
But, again, the belt of rains is so far from being a belt of calms strictly, that its monsoons in the Indian, Atlantic, and Pacific Oceans, at times, extend hundreds of miles out over the ocean. That of the Atlantic, triangular, with its base resting on Africa, according to Lieutenant Maury, extends sometimes almost to the coast of South America, a distance of one thousand miles, and thus under the supposed ascending vortex. Where is the great uprising suction during the prevalence of this extensive surface horizontal monsoon beneath it? Manifestly it does not exist. Nay, that monsoon is blowing from the warm current which sets up from the Cape of Good Hope toward the Caribbean Sea, and over the cold north polar current, which runs down between the continent and the Cape de Verdes. Equally untrue is the presumption that the air rises over heated portions of the earth elsewhere, and by reason of such heating.Perpendicular currents of the atmosphere are rarely seen, never extensive, or attaining any considerable altitude.I have watched for them thirty years. I have seen currents of air ascend, with their moisture condensing as they ascended, and unite with the under surface of a highly electrified cloud—the advance condensation of a thunder shower—but that cloud was moving horizontally at a distance of from one to two thousand feet above the surface of the earth, and did not rise. I have seen patches of scud rising from the surface during the intervals of a showery and highly electrified storm, toward, and uniting with, the clouds above, when very low, as I have seen them approach and unite horizontally; and doubtless there is a tendency upwards of the wind, created and attracted by the summer shower, as may be seen in the ascending dust before the rain, but I have never been able to detect an ascending current, except as induced and attracted by a cloud above moving horizontally, in the hottest day or dryest time. None of the clouds of our climate, even when the earth is heated and parched by a two months’ unbroken drought, can be detected rising above the strata in which they form. I have watched the cumuli at such periods when they filled the air, and can assert that they never rise. The atmosphere moves, invariably, in horizontal strata, and the whole theory of ascending currents is fallacious.
But let us look still further at the tropical currents. The true harmattan of north-western Africa (for the term is sometimes misapplied), hot and blistering,generated upon the sand of the desert—why does it blow from Sahara horizontally, on or over cooler surfaces, following the belt of rains as a N. E. trade? Why does it not ascend? The sirocco of north Sahara, the kamsin or chamsin of eastern Sahara, and the simoon of Arabia, which blow hot and suffocating from those deserts—why do they blowfromheated surfaces andhorizontally overcooler ones? Why do they not ascend? Arabia is surrounded on three sides by seas and gulfs, from which evaporation is rapid. Her interior deserts are extensive and intensely hot—why are they rainless? Why do they not have avortex, amonsoon, or even ashower? Because there is no such law or action as this theory supposes. Those winds blow horizontally in obedience to other laws, and under the control of other and more powerful agents. But further still, what heating and ascending process is it that makes the variable winds north of the tropics? that brings in the warm air and fog of the Gulf Stream upon oursnow-clad coast, in mid-winter, to increase the January thaw? Nay, what heating process is it that disturbs the calms of the polar regions with fresh breezes and gales, sometimes of the force of 6, when thesun does not shine, the thermometer is from 20° to 40° below zero, theearth and sea one frozen surface, and the hardy explorer dressed in furs, barely lives in his cabin covered by an embankment of snow, and heated by a stove?
Gentlemen, meteorologists, it will not do. The theory is unsound; the assumed facts do not exist.The whole universe has not an agent, organic or inorganic, which can play such absurd and inconsistent pranks in the face of its Creator, as your various and complicated theories assign to caloric.
Away with the theory and all its incidental and complicated and mystified hypotheses, they rest like a pall upon the science;—away with the whole system, and let us seek some agent whosepowerandadaptationcorrespond with theextent, andsimplicity, andmagnificenceof the phenomena, and, in some degree, with thepowerandwisdom of their Author.
One, and the principal end attained by the power of the agent, is the gathering of a volume of atmosphere from, or near, thesurfaceof the land and sea, so as to ensure its possession of all the moisture of evaporation which rises from the locality, and the highest degree of temperature, and from a space ranging from one to two thousand miles in width, in one hemisphere, and to carry it over into the other. Not over the top, or upon the top, of the whole mass of atmosphere situated in the opposite hemisphere—out of reach of all influences from the earth—but through it, and curving gradually down near to, and within influential distance of the surface of the earth, soon after it passes the outward limit of its fellow trade; and to continue the current onward, leaving portions of it and its heat and moisture on the way, but taking a considerable volume up and around the magnetic poles—it being impossible for the entire volume to be thus carried around the poles in consequence of the diminished circumference of the earth. To this end it is obvious it must possesspolarity.
Another end to be attained is to combine the moisture of evaporation with the air, so that the coldatmosphere through which, or the earth over which it passes, may not becontinually condensing its moisture, and therebyenveloping the earth in a perpetual mist; but so that it may part with it atintervals, makingcloudyandclear days; and part with it inportions, so that aregularandnecessary supplymay be furnished to theentire hemisphere, even up to the geographical poles. Is there such an agent? There is, precisely and perfectly adapted to the ends to be attained, ever there and ever active, and that agent ismagnetism.
Fig. 12.
The earth is a magnet. It has its magnetic poles, and they are distinct from its geographical ones; and there are two in each hemisphere. They are situated from 17° to 19° distant from the geographical poles; and ours is not far from longitude 97° W. from Greenwich, and 71° north latitude. Navigators have gone north and north-west of it, and found its situation by the declination of the needle. From these poles, lines of magnetic intensity extend to the opposite and corresponding pole of the otherhemisphere, and upon or near those lines the needle points north without variation; and toward these lines of no variation the needle every where, on either side declines. The foregoing diagram shows the situation of our magnetic pole and line of no variation, the dip of the needle by the arrows, and the magnetic equator.
Recent discoveries have shown that the magnetic force is exerted in lines and currents; that such currents, as physical lines of force, surround magnets, and currents of electricity. Doubtless such lines of force exist around the earth and the magnetic poles. There are alsolongitudinallines of force existing and active, between the poles, and extending from one side of the center to the other, occupying nearly one third of the magnet. If you take a large needle thoroughly magnetized, place it upon paper and drop filings of iron upon it, they will become arranged about it in circular and perpendicular, and also inlongitudinal lines, conforming to the currents.
Fig. 13.
This experiment is illustrated in all our books on natural philosophy.
The foregoing diagram, copied from Olmstead’s Philosophy, does not show as accurately asFaraday’sprojection of the lines upon a globe-magnetthe comparative distance from the poles of the needle, at which the longitudinal currents commence and terminate, andwhere the filings will not adhereto any considerable extent. The lines shown upon the needle should bear the same proportion to its length as the trade-winds bear to that of the earth, measured from pole to pole, and if the needle had a globular form they would so appear.
These lines are made by currents arising from one side of the magnetic equator, and passing over to the other. Doubtless, just such currents rise, and pass over upon the earth.
Magnetic and electric currents carry the air with them. This is well settled by experiment.Oxygen, too, ismagnetic, and capable both of receiving and retaining polarity and of combining with, or attracting and retaining vapor, and of course the moisture of evaporation. Here then we have a power existing, capable of producing the result—precisely, and with evident wisdom adapted to its production—ever present and active; and no other known agent can.
Is it not then the agent?
Let us look a little further. This result is affected by the action of the sun: the trades with the central belts of rains travel north and south after it; so does the sun affect the magnetic currents every where, even the magnetic needle is daily affected by its action, as it increases the intensity of the terrestrial magnetic currents, and hence its well established diurnal oscillations.
Again, along the eastern lines of the continents which skirt the great oceans on the west, run the northerly and southerly lines of no variation, and of greatest magnetic intensity. Here are the trade currents gathered into a volume, which curve and carry unusual fertility to South-eastern Asia, and North America, and in those great aerial gulf streams we find theintenseelectric action which produces the typhoons of the former, and the hurricanes of the latter. It may still be said that these conditions and phenomena of the trade-wind region, are not produced by magnetism or magneto-electricity,but the objector can point to no other adequate power. That it must be heat, electricity, or magnetism, must be admitted. There is no other power known. Heat demonstrably can not produce them. Magnetism or electricity therefore must, and they are doubtless states or phases of the same power, producing in their different states or phases the different results. And even heat—atmospheric temperature, is often, if not always the result of their action. In the present state of science, it is enough for me that themagnetic longitudinal currents are there; that they arelines of forceandadequate; thatoxygen is magnetic, and therefore the atmosphere must be affected by them—that so far as we can reason from analogy, they ought to produce the effect upon the atmosphere which we find produced, and until further light is thrown upon the subject I shall presume that they do. Every step we take hereafter in this investigation will confirm the presumption.
There is one peculiarity to be more particularly noticed before we leave the trade-wind region, and we are now prepared to notice it.
The belt of rains, formed by the currents of the two trades, threading their way through each other—how are they produced? Why should the place where the currents thus pass through each other be a place of almost daily precipitation? There is, in fact, no ascension, except that which the currents have in their line of ascent to attain the elevation which the magnetic law of the current requires.
The trades have passed over an evaporating surface and are charged with moisture. This moisture they hold in magneto-electric combination.Evaporationdoes not depend upontemperature. Ice and snow evaporate at all temperatures (Howard, vol. 1, p. 86). So the cold N. W. wind, full of positive electricity, will lap up, as it were, the pools from the earth, with astonishing quickness; and when this electricity is deranging the action of the machinery and material of the manufacturer, he allays it by a supply of moisture, with which the electricity can combine. Nor does the air lose its moisture when below the freezing point. In all parts of the atmosphere, as at the surface of the earth in winter, moisture is held in large quantities in the coldest and severest weather; and it is not till it moderates, and a perceptibleelectricchange takes place, that it is precipitated as rain or snow. Doubtless there is an exposure of considerable surfaces, of opposite currents, charged with opposite polarity, and a constant depolarization wheretheir surfaces meet. May there not be a consequent dissolution of the electro-magnetic combination between the air and moisture, or the excitation of that electric action which attends or produces like rains every where? and hence the constant precipitation. This is rendered probable, by the fact that precipitation, at the meeting of the trades, takes place in level countries in the day-time, between 10A. M.and sunset, in showers, with thunder and lightning, as with us in summer, although among the mountains the rain sometimes falls in the night also. The precipitation in the heat of the day is obviously induced by the action of the sun, although it is by no means certain that the friction of the opposing surfaces does not assist in the operation.
I am well aware that the lines of magnetic force curve upward and carry the trades with them, and that, therefore, precipitation by condensation from the mere cold of the upper stratum of the atmosphere is possible. But, there are three reasons why I do not believe such to be the fact.
1st. Precipitation takes place in the day time mainly, and in sudden, isolated, heavy showers and not in steady continuous rain. Nor is there condensation or continual mist at other hours of the day.
2d. They occur at a time of day when the sun is affecting the magnetic currents most powerfully,viz., between ten o’clockA. M.and sunset, and mainly at the time of greatest heat.
3d. The counter-tradesdo not precipitateafter they leave the rainy belt, although at a great elevation,until they reach the outward limits of the trades; and theydo precipitate again, although they gradually descendnearer the earth, as soon as they become subject to the action of the currents of an opposite magnetism. Their precipitation is partial too, even then, and they carry a portion of their moisture through an atmosphere of the coldest temperature up to the geographical poles.
A similar result attends the action of the sun in the extra-tropical regions. Cumuli commence forming in the counter-trade, or at the line between that and the surface current, at the same time of day that the diurnal motion of the magnetic needle commences, or the rain clouds form in the tropics; they continue to enlarge here as there, till about the same hour of the day that theneedleobtains its maximum diurnal variations; and when the influence of the sun upon the needle ceases, and it returns to its original status, the cumuli disappear. Hail storms too, it is said, always, or generally occur in the day time.
In like manner the sea-breezes and other fair-weather surface winds, rise in the forenoon with the influence of the sun upon the magnetic currents and the needle, and die away at nightfall when the influence ceases.
There are other electro-magnetic, or to speak more correctly, magneto-electric, effects of the sun’s action equally illustrative, which tend to show that the precipitation at the passing of the trades, is the result of their action upon each other, aided by the sun, towhich we shall allude when we come to speak of the causes and character of the surface winds of the extra-tropical regions.
As, however, this takes place only, or mainly, where the threading surfaces meet, it is but partial, and the body of the respective polarized currents pursue their way unaffected, toward the opposite magnetic pole—and there for the present we leave them.
Storms sometimes originate in these currents, when concentrated, as in the West Indies, the China Sea, the Bay of Bengal, and Indian Ocean, while passing through the rainy belt, and move with the current to the north-west if issuing on the north side of it, and to the south-west if issuing on the south side of it, until they respectively get beyond the extreme limits of the trades, and then they curve to the eastward, imbedded in and following their current. The peculiar extension of the land to the east on the northern portions of South America, prevents the gathering of an aerial gulf similar to the one which we have described to the north-west, entering upon our division of the continent over the Gulf of Mexico. It is otherwise in the Indian Ocean, and there the storms are found issuing from the rainy belt on the southern side, sweeping over the Mauritius and other islands of that ocean, andoften simultaneouslywith storms issuing on the north over the Bay of Bengal. Colonel Reid mentions instances and gives a diagram.[2]
These storms in milder forms issue from the rain belt at other points, and may issue any where, but will always be found most extensive and most violent, that is to say, as hurricanes and typhoons, in the concentrated volumes of counter-trade on the western side of the great oceans, within a few hundred miles of the lines of magnetic intensity and no variation, and when they form in the rainy belt they are highly electric. Most frequently, however, as we shall see, they form in these currents after they have issued from the rainy belt, and after they have passed the extreme limits of the trades and become subject to the circular and perpendicular magnetic currents which exist north and south of the longitudinal ones, and which when seen upon the magnetic needle, attract the filings and cause them to adhere—although but slight attraction or adhesion takes place where the longitudinal currents exist.
Such, then, are the atmospheric arrangements and phenomena of the trade-wind region, and the cause that produces them; such is the character and cause of the enlarged volume of counter-trade, which spreads out and blows over our country as permanently as the S. E. trades blow on the South Atlantic and South America, returning to us the rivers which had run from us to the sea.
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 overMadeira, 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 arepreceded 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, theirsouth-westbeing aclearing off windas ournorth-westis, andprecisely 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 oceanover mountain rangespart 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 NorthernMexico, and in summer, and while the belt of the tropics is extended up over them, they have rain and in daily showers whichtravel 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°, and in this also thosegentlemenare 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, gatheredby 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 formonths 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 theirway to enter the central belt. So blow the N. E. trades from the Mediterranean, and the Barbary Statesover the Desert of Saharaand 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 otherwhollyrainless 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 ofS. 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 thatregion. (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, andwithout the existence and influential agencyof a counter-trade; and thatreciprocal action, whatever it may be, that takes placebetween it and the earth.
Again, our own experience is conclusive of this. We have no surface-trade north of 30°, and yet a long drought and great evaporation may follow a wet spring. Belts of droughts and frequent rainsoccur every year in different portions of the country side by side, andthe 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 condensationwhich 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, orwithin 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-atmosphereinducedby 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 condensationis 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 whichthe sun istoofar 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.