The Philosophy of the Weather Part 11

1st. The deserts of Cobi and Bucharia, which const.i.tute the "burning plains" of _Central_ Asia, north-east of the Indian Ocean, lie between 38 and 45 of north lat.i.tude, and under the zone of extra-tropical rains.

They are not wholly rainless. They partake of that saline character which affects so much of Asia and the western part of this continent. South of them, running nearly east and west, are the lofty ranges of the Himmalaya and Kuenlun Mountains, and the table lands of Thibet. To their saline character, in part, but mainly to the interposition of these mountain ranges, depriving the counter-trade of moisture, they owe their comparative sterility. _If bountifully supplied with rains, this salt would doubtless ere this have been washed to the ocean, as it has been from other countries, once as salt as they._ But they have some rain, and more or less vegetation, and are not intensely hot. They lie too far north, and are too elevated. Their temperature is not materially different from that of the western, and comparatively desert portions of our own country, and they are utterly incapable of creating a monsoon at the Indian Ocean, and especially from the long line of Malabar coast, where the south-west monsoons are found in most strength. The sterile portions of Utah, New Mexico, and Texas are alike incapable of such effect upon the atmosphere of Central America and Mexico. These monsoons commence in May, and prevail until October, and the temperature of the air where they blow ranges with considerable regularity between 76 at night, and 84 at mid-day, on the Malabar coast, and a trifle lower in Central America.

At Fort Fillmore, El Paso, New Mexico, in lat.i.tude 3203, the mean temperature for

May is 68 June " 78, 5'

July " 80, 1'

August " 83, 8'

September " 77, 9'

------- And for the whole period, 77, 1'

At Santa Fe, New Mexico, the mean for May is 66, 9'

June " 72, 5'

July " 75, 3'

August " 72, 9'

September " 62, 3'

------- And for the whole period, 69, 3'

Mean of the two united, 73, 2'

The mean of Western Texas is about 2 higher than at Fort Fillmore, and of Utah not materially different; and the mean of _Central_ Asia between 38 and 45 does not materially vary from them.

Now, it is perfectly evident that during May and September the temperature of Central Asia is far below that of the Indian Ocean and India, and never materially exceeds it. Central Asia is hot, "burning," if you please, compared with more elevated, fertile, or better watered territory _in the same lat.i.tude_, and so it has been characterized; but not so, compared with the Indian Ocean, or India, where the sun is vertical. During the greater part of the time, therefore, that the monsoons are in full blast, Utah, Texas, and New Mexico, and Cobi, and the burning plains of Asia, are from 5 to 10 colder than the temperature of the place where the monsoons are blowing. Would not such a fact be perfectly conclusive in any other science except theory-swathed meteorology?

2d. The theory a.s.sumes that the heated air has an ascensive force, which causes it to rise and create a vacuum, and this vacuum, by its suction, draws in the adjoining air, which immediately ascends. The adjoining air, drawn away from its locality, leaves a vacuum, and that is filled by another rush from the S. W., and so on, till the Indian Ocean is reached, and the monsoons are accounted for.

Now, look at the difficulties:

The highest temperature that can be a.s.sumed for the air over Cobi, at any time, without disregarding facts and a.n.a.logy, is 100. What is the ascensive power of an area of atmosphere of 100? For this we have no problem or formula, although problems and formulas abound in the science.

Professor Espy relied on heated air only to give the storm a _start_. His main reliance was on the latent heat supposed to be given out during condensation, for his ascensive storm power. But over these "burning plains" there is, according to the theory, no storm or cloud, or condensation on which that supposed reliance for expansion can be placed.

What, then, is the ascension force of air at 100? _We ought to know, for we sometimes have it as high, or within two or three degrees as high, in all the eastern and middle States._

The monsoons blow at from twenty to twenty-five miles an hour, and sometimes more. Is that the ascensive force of air at 100? At 25 miles an hour it would be 2,200 feet; at 20 miles, 1,760 feet; and at 10 miles, 880 feet per minute.

Does any man believe that either current exists? Why, then, do we not have our hats taken off, or light objects carried up, or have a monsoon, or, at least, have the clouds running up, when we have such elevated temperatures. _Nothing of the kind occurs with us._ Our hottest days are comparatively still days; and I have seen the c.u.mulus sailing gently to the east, horizontally, when the air was at 98. Why should we be exempt?

Is not our air the same and our heat the same?

Again, suppose we grant that the ascensive force is equal to 20 or even 10 miles an hour, will not the adjoining air hold back somewhat to avoid leaving behind an entire vacuum? or, will it all voluntarily rush in, and leave a new complete vacuum? and, if so, why the preference of vacuums by the air, and _when, where, and why_, should the _successive vacuums stop_?

Nay, would not gravity fill the second vacuum from _above_, rather than from the south-west side? and will not the air incline to rush in, to some or all these successive vacuums, from some other side than south-west? or, have these deserts the power of selecting the quarter from which their vacuum shall be filled, and of delegating it to succeeding vacuums? Would it not incline to rush in from the east and west where there are no elevations, rather than from the S. W. and over the Kuenlun Mountains, the intervening ridges and valleys of Thibet, the lofty Himmalayas, the extent of India, and the Ghaut Mountains, from three to four thousand feet high, on its eastern coast? Would it not, at least, _leak in a little_, and lessen the force with which the vacuums would draw from the far-off Indian Ocean, so that the monsoon could not blow with equal force? or, if Cobi and its fellow deserts _must_ and _can_ draw from an _ocean_, why not from the head of the Arabian Sea, or Bay of Bengal, or the China Sea, which are nearer, or from the j.a.pan Sea, which is still nearer, or the Yellow Sea, which is close by? Why draw only from under the central belt of rains?

Nay, what shall be done with Professor Dove? In a recent article, republished in the American Journal of Science and Art, for January, 1855, he says: "A greatly diminished atmospheric pressure taking place in summer over the _whole continent_ of Asia must produce an influx from all surrounding parts; and thus we have west winds in Europe, north winds in the Icy Sea, east winds on the east coast of Asia, and south winds in India. _The monsoon itself becomes, as we see, in this point of view, only a secondary phenomena._" This looks very like _antagonism_. Who shall we believe?

Again, suppose you get one atmosphere from the whole area, raised up by the supposed ascensive force, and at the rate of twenty-five, twenty, or even ten miles an hour, and a new volume drawn in from the south-west, and _over the mountains_: will it not take a _little time_ for _that_ to _heat up_? Does it heat so fast as to _keep up the ascensive force_ without intermission, at twenty-five, or twenty, or ten miles the hour?

What says Mr. Ericsson to this? Can he not arrange with a moderate lens, to move his engine with the rays of the summer sun? Nay, Lieutenant Maury says they can not heat up "_per saltum_, or in a day." But according to a reasonable calculation, they must heat up the air from 80, or less, to 100, at the rate of 2,000 feet per minute. Heating 2,000 feet in depth, in the proportion of 20 per minute, night and day, for five months, is "_per saltum_" in a minute, and 1,440 "_saltums_" per day!

And further still, the Indian Ocean, from which the monsoons are drawn to Cobi and Central Asia to the N. E., is during those months covered by the belt of calms and rains, as heretofore stated; and the S. E. trades blowing into it are attributed to the suction created by the ascent of heated air _there_. So, then, the monsoons are blowing away from under the rainy belt, from 500 to 1000 miles, to Cobi and the burning plains of Asia, while the ascensive force of that belt is such as to draw the S. E.

trades toward the very spot, a distance of 1,200 or 1,500 miles, at 20 miles an hour! What must the ascensive force over Cobi, etc., be, if, as a "stronger power," it can overcome an ascensive force over the Indian Ocean sufficient to draw the S. E. trades 1,500 miles, at 20 miles an hour; and, in addition to the force necessary to resist this central suction, not only stop or hold back the N. E. trade, but reverse it and draw it back, at 20 miles an hour, as a monsoon? Must it not be, at least, double that of the belt of calms, or the "great region of expansion," as Professor Dove calls it?

Now, I am irresistibly tempted to ask whether a meteorological theory can be too absurd for credence, and whether it would not be as well to endow the deserts with ribs and lungs, and a proboscis long enough to reach the Indian Ocean, and the necessary power of inspiration and expiration? Such a theory would avoid all difficulties, conflict with no more a.n.a.logies, and, in my judgment, be as much ent.i.tled to credit as the one to which meteorologists adhere.

3d. North of the Malabar coast, in the north-west of India, lies an extensive desert. West of that is Beloochistan, with its rainless deserts.

Further west are the rainless deserts of Arabia, and these three, including the Persian deserts further north, cover _as much surface_ as the deserts of Cobi and Bucharia--have the sun vertical in part, and nearly so over the entire surface--_are more intensely hot_, and lie within _one third of the distance_ which intervenes between that desert and the Indian Ocean off the Malabar coast, with _an open sea and_ no _mountains between_. Now, look at it. The north-west desert of India, and the rainless deserts of Beloochistan and Arabia _reverse no trade_ and _have no monsoon_, although the Arabian Sea heads right up among them.

They do not attract one from the Indian Ocean off the Malabar coast, although not more than one third of the distance off, and without such mountains and table lands intervening as separate that coast from Cobi. It is said by Lieutenant Maury that the monsoons, "_obey the stronger force_." But which is the stronger force? Cobi, not _wholly_ rainless, lying north of 35, under the zone of extra-tropical rains, with India and the Ghauts, the Himmalaya Mountains, the table lands of Thibet, and the Kuenlun Mountains between? or the deserts of India, Beloochistan, and Arabia, _wholly rainless_, and _intensely hot, near by_, and in _open view_. There can be but one answer to this question. Nothing in the way of desert barrenness, or elevated temperature, unless it be those of Sahara, can exceed the deserts about the head of the Arabian Sea and Persian Gulf.

Certainly those of Cobi can not compare with them; yet the trades blow steadily over them, although more northerly there, as every where, near their northern limits, especially on land. Says Hopkins, in his atmospheric changes:

"If any one part of the broad expanse of the continent of Asia could be heated so as to draw air from the Arabian Sea and the Indian Ocean during the summer, it would be that part which lies between Hindoostan and the Lake of Aral, including the region between the Valley of the Oxus and Persia, and the land of this part, unlike Hindoostan, is not screened from the sun by thick vapors. But what says Burnes respecting the winds of this part? Why, that about the latter end of June, though the thermometer was at 103 in the day, 'In this country a steady wind generally blows from the north.' And on the 23d of August, after having pa.s.sed the Oxus--'The heat of the sand rose to 150, and that of the atmosphere exceeded 100, but the wind blew steadily, nor do I believe that it would be possible to traverse this tract in summer if it ceased to blow. The steady manner in which it comes from one direction is remarkable in this inland country.' Again--'The air itself was not disturbed but by the usual north wind that blows steadily in this desert.' And he has many other similar pa.s.sages."

Here there is a vast tract of country south of 35 which has a temperature often of 103, and does not reverse the trade and create a monsoon. How utterly unphilosophical, then, to attribute the monsoons to Cobi because they "obey the stronger force!" or to attribute them to it at all.

4th. The monsoons can not be _traced from_ the Malabar coast _to Cobi_.

They do not exist on the south-west of Cobi and near it, where they should in greatest force, and there is no connection, in fact, shown between them. They do not often extend more than twenty-five miles inland, or to the east of the Ghauts. There are no corresponding intervening monsoons crossing India to the mountains--none over the mountains and table lands--none under the northern lee of the mountains--nor, in short, on the whole track, nor any S. W. winds except such as naturally belong to the action of the curving counter-trade.

Finally, the investigations of Commodore Wilkes on Mauna Loa, a mountain upon Hawaii, more than 13,000 feet high, and the observations of Professor Wise and other aeronauts are sufficient to put this whole matter of heated lands and ascent of the atmosphere as the cause of winds, at rest.

Commodore Wilkes was encamped for about _twenty days_ on Pendulum Peak, in December and January 1840. Although not up to the elevation of the counter-trade in that lat.i.tude, he was above the local clouds which form over the island during the day, where the sea breezes blow in with as great strength as any where. Indeed, he was on the top of the "lofty conical mountain" to which Caleb Williams alludes in the letter to Professor Espy I have quoted, and above the spot where Professor Espy a.s.sumed that the clouds were rising with such force as to induce the strong sea breezes of that island. During this time there were two snow-storms on Mauna Loa, and they had the wind from the S. W. during the storm, as might be expected, looking at the situation of the mountain on the western side of the island. These storms moved to the N. W., and were observed at the other islands in that direction as rain.

The local clouds lay over the island every day, as they do over active volcanic islands which are very elevated, although it was the dry season.

_Nothing like an ascent of the clouds or of the currents of air from the ocean was observed._ On the contrary, the clouds formed before the sea breezes set in, and the latter blew from the different sides of the island in under the clouds, and outward again, probably on the opposite side. The whole interior of the island is elevated, and its temperature low; and _there was no elevation of temperature on the high portions of the island over which the clouds formed, and toward which the winds blew, which could create an upward current_.

"During our stay on the summit, we took much pleasure and interest in watching the various movements of the clouds; this day in particular, they attracted our attention; the whole island beneath us was covered with a dense white ma.s.s, in the center of which was the cloud of the volcano rising like an immense dome. All was motionless until the hour arrived when the sea-breeze set in from the different sides of the island; a motion was then seen in the clouds, at the opposite extremities, both of which seemed apparently moving toward the same center, in undulations, until they became quite compact, and so contracted in s.p.a.ce as to enable us to see a well defined horizon; at the same time there was a wind from the mountain, at right angles, that was affecting the ma.s.s, and drawing it asunder in the opposite direction. The play of these ma.s.ses was at times in circular orbits, as they became influenced alternately by the different forces, until the whole was pa.s.sing to and from the center in every direction, a.s.suming every variety of form, shape and motion.

"On other days clouds would approach us from the S. W. when we had a strong N. E. trade-wind blowing, coming up with c.u.mulus front, reaching the height of about eight thousand feet, spreading horizontally, and then dissipating. At times they would be seen lying over the island in large horizontal sheets as white as the purest snow, with a sky above of the deepest azure blue that fancy can depict. I saw nothing in it approaching to blackness at any time."

(Exploring Expedition, vol iv. p. 155).

Here, in the last paragraph, we have the whole truth disclosed. The N. E.

trade was blowing on Mauna Loa, 13,000 feet above the sea, and the sea-breeze blew in on the _leeward side_, its moisture condensing over the volcanic island, but without rising _up the mountain_, or _through the surface-trade_, or _above 8,000 feet_.

So, too, the celebrated aeronaut, Mr. Wise, in the course of more than a hundred ascensions, some during high wind, and others during rain storms, never met with an ascending current, except in a single instance, in the body of a hail-cloud, and then there were descending currents also, the usual intestine motion of hail-cloud with its opposite polarities.

I copy a description of his pa.s.sage through the clouds of a rain-storm, and his floating a long period above them; and there was no ascending current which disturbed their horizontal repose or progression. The double layer is not uncommon--condensation taking place at the connection of the upper and lower portions of the trades, with the surrounding atmosphere; or in the trade, and by _induction in the surface atmosphere_ at the same time. Such instances are frequently visible, and if his ascensions had been undertaken at other times in stormy weather he would have seen more of them.

"Before I pa.s.sed the limits of the borough, a parachute, containing an animal, was dropped, which descended fast and steady, and, just as it reached the earth, my aerial s.h.i.+p entered a dense black body of clouds. Ten minutes were consumed in penetrating this dismal ocean of rainy vapor, occasionally meeting with great chasms, ravines, and defiles, of different shades of light and darkness. When I emerged from this ocean of clouds, a new and wonderfully magnificent scene greeted my eyes. A faint suns.h.i.+ne shed its warmth and l.u.s.ter over the surface of this vast cloud sea. The balloon rose more rapidly after it got above it. Viewing it from an elevation above the surface, I discovered it to present the same shape of the earth beneath, developing mountains and valleys, corresponding to those on the earth's surface. The profile of the cloud-surface was more depressed than that on the earth, and, in the distance of the cloud-valley a magnificent sight presented itself. Pyramids and castles, rocks and reefs, icebergs and s.h.i.+ps, towers and domes--every thing belonging to the grand and magnificent could be seen in this distant harbor; the half-obscured sun shedding his mellow light upon it, gave it a rich and dazzling l.u.s.ter. They were really "castles in the air," formed of the clouds. Casting my eyes upward, I was astonished in beholding another cloud-stratum, far above the lower one; it was what is commonly termed a "mackerel sky," the sun faintly s.h.i.+ning through it.

The balloon seemed to be stationary; the clouds above and below appeared to be quiescent; the air castles, in the distance, stood to their places; silence reigned supreme; it was solemnly sublime.

Solitary and alone in a mansion of the skies, my very soul swelled with emotion; I had no companion to pour out my feelings to. Great G.o.d, what a scene of grandeur! Such were my thoughts; a reverence for the works of nature, an admiration indescribable. The solemn grandeur--the very stillness that surrounded me--seemed to make a sound of praise.

"This was a scene such that I never beheld one before or after exactly like it. Two perfect layers of clouds, one not a mile above the earth; the other, about a mile higher; and, between the two, a clear atmosphere, in the midst of which the balloon stood quietly in s.p.a.ce. It was, indeed, a strange sight--a meteorological fact, which we cannot possibly see or make ourselves acquainted with, without soaring above the surface of the earth." (History and Practice of Aeronautics, p. 209).

This is graphic. Perhaps in relation to the conformity of the upper surface of the inferior layer of clouds, to the irregularities of the earth's surface, he was misled during the enthusiasm of the moment. He is certainly mistaken as to the possibility of observing these double layers from the earth; I have seen them in hundreds of instances. But in relation to the _quiescence_ of the clouds for an hour, and _the entire absence of ascending currents_, he could not be mistaken.

And now, in the absence of all direct proof to sustain the hypothesis, that the heating of the land produces ascending currents, and thereby the winds, and especially the monsoons, and in view of all the adverse evidence, I put it to Lieutenant Maury, and every sincere searcher after meteorological truth, whether the theory should not be abandoned.

CHAPTER VII.

The counter-trade of the northern hemisphere ranges at different heights in different lat.i.tudes, in the same lat.i.tude at different seasons, and also upon different days of the same season; and, like the line of perpetual snow, has its greatest elevation in the tropics, descending gradually to the surface of the ocean at the poles. At the northern limit of the N. E. trades, it does not, ordinarily, approach the earth sufficiently near for decided reciprocal action. Hence, at that point, storms do not often originate; the winds are lighter and more variable, and calms are more frequent than at any point, except at the meeting and elevation of the trades, or in the polar regions. Doubtless this state of things is increased by the feebler action of north polar magnetism, and the irregular action of the longitudinal magnetic currents, evinced by the irregular, and often, feeble action of the trades, near their extreme limits. They are not unfrequently wholly wanting, near the northern limit, for several days in succession, and calms and baffling winds are found in their place--another effect of the irregular action of terrestrial magnetism, consequent upon the ever-changing transit of central activity from south to north, and from north to south. Upon the islands, however, and continents, which have elevated mountain peaks and ridges, especially if of volcanic origin and activity, which approach more nearly the path of the counter-trade, a different state of things exists. There, showers and gusts are frequent. Thus, upon the Sandwich Island, Kauai, the most northern one, which is within the region of the N. E. trade during ten months of the year, and upon its volcanic peaks and elevated table-lands, and north-easterly from them, over the district of Waioli, rain falls in abundance during the year, while the coastlines upon other portions of the island can not be cultivated without irrigation. (See Wilkes' Exploring Expedition, vol. iv. pp. 61 and 71; and American Journal of Science and Art, for May, 1847).

A like state of things, in degree, may be found upon the Canaries, and the more elevated of the West India Islands. The Cape de Verdes are an exception, and the Christian world are quite often called upon for contributions of provisions, to save the inhabitants of these islands from starvation. They lie at the northern limit of the equatorial belt, and for a period of two months only (July and August), are supplied with rain. If, from any cause, the belt does not move as far north as usual during any season, unbroken drought and famine are sure to overtake them. The islands contain some elevated peaks, and are of volcanic origin, but not of present volcanic activity, and the counter-trades as they issue from the equatorial belt at their highest elevation, are too far above them for reciprocal, influential action. If the islands could be placed 10 further north, we should hear no more of drought or famine from them, and their quant.i.ty of rain and fertility would be not only more permanent, but much increased. Superadded to this, is the fact, that at that point the belt of rains precipitates feebly because the S. E. trade originates upon the southern part of the continent of Africa, and the N. E. mainly, upon the desert and the Barbary States--and both are sparingly supplied with moisture.