Outlines of a Mechanical Theory of Storms Part 8

[19] It is worthy of notice here, that New York, which only differs by about 40 miles of lat.i.tude and 800 in longitude, had the storm earlier, near the time of the pa.s.sage, as appears by the appended account of it.

This proves, that a storm affects a particular lat.i.tude simultaneously, or approximately so. If this had to travel eastward to reach New York, it would have been the 10th instead of the 8th. The princ.i.p.al trouble was, however, in the early part of the evening of the 8th, to the south of Ottawa, where the strong wind was drawn in from the northward. If a vortex pa.s.ses from north to south, leaving the observer between the pa.s.sages, there must, nearly always, be a winding up squall from the north to clear away the vapory atmosphere.

[20] From the _New York Tribune_, July 9, 1853.

[21] These pages are now in the compositors' hands, (Nov. 21st,) and up to the last moment the Author has observed carefully in New York the pa.s.sages of these vortices. October 24th, in the inner vortex descending produced a violent storm on the coast, and much damage ensued. November 7th, the same vortex ascending was also severe. And on November 13th, early, the pa.s.sage of the central vortex ascending, caused a flood in Connecticut of a very disastrous nature. Would it not pay the insurance offices to patronize such investigations in view of such palpable facts as these?

SECTION THIRD.

OBJECTIONS TO LUNAR INFLUENCE.

We have now presented a theory of the weather, which accounts for many prominent phenomena, a few of which we shall enumerate. It is an observed fact, that in all great storms electrical action is more or less violent, and that without this element it seems impossible to explain the velocity of the wind in the tornado, its limited track, and the formation of large ma.s.ses of ice or hail in the upper regions of the atmosphere. It is also an observed fact, that the barometer is in continued motion, which can only be legitimately referred to a change in the weight of the atmospheric column. This we have explained as due to atmospheric waves, caused by the greater velocity of rotation of the external ether, as well as to the action of the three great vortices.

These causes, however, only partially produce the effect--the greater portion of the daily oscillations is produced by the action of the great radial stream of the solar vortex, as we shall presently explain. It is an observed fact, that, although the storm is frequently violent, according to the depression of the barometer, it is not always so.

According to the theory, the storm will be violent, _ceteris paribus_, on a line of low barometer, but may still be violent, when the contrary obtains. Another fact is the disturbance of the magnetic needle during a storm. Storms are also preceded generally by a rise in the thermometer, and succeeded by a fall; also by a fall in the barometer, and succeded by a rise. It is also well known, that hurricanes are unknown at the equator, and probably at the poles also. At all events, they are rare in lat. 80, and, according to Capt. Scoresby, storms are there frequently raging to the south, while above, there is clear sky and fine weather, with a stiff breeze from the northward. The greater violence of storms in those regions where the magnetic intensity is greater in the same lat.i.tude, the probable connection of peculiarities in the electric state of the atmosphere with earthquakes, and the indications of the latter afforded by the magnet; the preponderance of westerly winds at a great elevation in every lat.i.tude on the globe visited by man; and the frequent superposition of warm layers of air above cold ones at those elevations, are all facts worthy of note. And the connection of cirrus clouds with storms, as well as with the aurora, indicates that the producing cause is external to the atmosphere, and gradually penetrates below. The theory fully explains this, and is confirmed by the fantastic wreathings and rapid formation of these clouds in straight lines of a hundred miles and upwards. But time would fail us in pointing out a t.i.the of the phenomena, traceable to the same cause, which keeps our atmosphere in a perpetual state of change, and we shall only advert to one more peculiarity of the theory. It places meteorology on a mathematical basis, and explains why it is that a storm may be raging at one place, while in another, not very remote, the weather may be fine, and yet be dependent on the position of the moon.

That the moon has exerted an influence on the weather has been the popular creed from time immemorial; but, ignorant of the mode in which this influence was exerted, men have often been found who have fostered the popular belief for their own vanity or advantage; and, on the other hand, philosophers have a.s.sailed it more by ridicule than by argument, as a relic of a barbarian age. Not so with all; for we believe we are not wrong in stating, that the celebrated Olbers compared the moon's positions with the weather for fifty years, before he gave his verdict against it. He found the average amount of rain at the perigee about equal to the amount at the apogee, as much at the full as at the change, and no difference at the quadratures. But this fact does not throw a feather in the scale by which this theory is weighed. Popular opinions, of remote origin, have almost always some foundation in fact, and it is not much more wise to reject them, than to receive them. The Baron Von Humboldt--a man possessing that rare ingredient of learning, a practical common sense--observes: "That arrogant spirit of incredulity which rejects facts, without attempting to investigate them, is, in some cases, more injurious than an unquestioning credulity."[22] If a popular belief or prejudice be absurd, its traditional preservation for a thousand years or more may very well account for the absurdity.

The present system of astronomy still retains the motley garniture of the celestial sphere, as handed down from the most remote antiquity; and granting that ages of ignorance and superst.i.tion have involved the history of the different constellations in a chaos of contradictory traditions, there is no doubt at the foundation some seeds of truth which may even yet emerge from the rubbish of fable, and bear fruit most precious. That the zodial[23] signs are significant records of something worthy of being preserved, is prejudice to deny; and we must be allowed to regard the Gorgons and Hydras of the skies as interesting problems yet unsolved, as well as to consider that the belief in lunar influence is a fragment of a true system of natural philosophy which has become more and more debased in postdiluvian times. Amongst those who have not summarily ignored the influence of the moon, is Toaldo, a Spanish physicist, who endeavored to show the connection between the recurrence of warm and cold seasons, and the semi-revolution of the lunar nodes and apogee, and proposed six of those periods, or about fifty-four years, as the cycle in which the changes of the weather would run through their course. According to the present theory, it is not likely such a cycle will ever be discovered. There are too many secular, as well as periodic influences combining, to produce the effect; and the times are too incommensurable. Lately, Mr. Glaisher has presented a paper to the Royal Society, giving about fourteen years from observation. Others have lately attempted to connect the changes of the seasons with the solar spots, as well as with the variations of the magnetism of the earth, but without any marked result.

It may, however, be urged, that if the sidereal period of the moon be approximately a cycle of change, it would have been detected long ago.

One reason why this has been so long concealed, is the high lat.i.tude of the observers. Spain, Italy, and Turkey, are better situated than other European countries; but the scientific nations lie further north; and from these the law has gone forth to regulate more southern lands. In the United States, particularly in the great plains of the west, the weather can be better compared; not only on account of the lat.i.tude being more favorable, but also on account of the greater magnetic intensity of the western hemisphere.

It must also be remembered that there are in lat.i.tude 40, five or six distinct pa.s.sages of the disturbing cause in one sidereal period of the moon. If two of these periods are drawn closer together by the change of the elements, the interval between two others must necessarily be increased. Besides, the effect produced is not always the same, for reasons already adverted to. One vortex may be more violent one month, or for a few days in one month, while another may be more active the next. It may also happen that for several successive pa.s.sages, the pa.s.sage shall be central in one lat.i.tude, while two or three degrees north or south, another place shall be pa.s.sed by. In different months and in different years, as well as in different seasons of the year, the energy of the ether may be augmented or diminished. But it may be said, that, supposing the theory true, if its indications are so uncertain, it is of little value. By no means. It is true there are many things to be inquired into; but it is a great thing in this science to be able to take the first step in the right direction,--to find even the _key_ of the portal. It is a great stride to be able to say, a storm may happen at such a time, but cannot happen at another; that a storm, when raging, will go in this direction, rather than in that; that it will be central here, and less violent yonder; and when we consider its bearing on astronomical and other science, it is difficult to exaggerate its value to the world at large.

Again, it may be said that rain, and cloudy days, and fresh breezes, and even strong winds, sometimes occur, when the vortices do not pa.s.s centrally. This is true; yet only indicating that where the vortices are central, an unusual disturbance is taking place. But there is another cause, which was purposely omitted in considering the prominent features of the theory, in order not to enc.u.mber the question with secondary influences. By referring to Fig. 3, section 1, we see that the lateral vortices of the globe are continually pa.s.sing off to the southward, in the northern hemisphere, in a succession of dimples, and continually reforming. We will now represent this mode of action in profile, as it actually occurs in the ill.u.s.tration we have used.

The vortex pa.s.sing off from O, (Fig. 20,) although it does not actually reach the surface of the atmosphere, affects the equilibrium of the ether, and, for a short distance from the parent vortex, may cause an ascensional movement of the air. If to this is conjoined a northerly wind from the vortex, a band of clouds will be produced, and perhaps rain; but violent storms never occur in the intervals, except as a steady gale, caused by the violence of a distant storm. Thus, it will frequently be noticed that these vortices are flanked by bands of clouds, which pa.s.s southward, although the individual clouds may be moving eastward. Hence, instead of disproving the theory, they offer strong evidence of its truth; and could we view the earth from the moon with a telescope, we should no doubt see her beautifully belted.

[Ill.u.s.tration: Fig. 20]

But it may be again asked, why should not the weather be the same generally, in the same lat.i.tude, if this theory be true? If the earth were a globe of level land, or altogether of water, no doubt it would be similar; but it must be remembered, that both land and water are very unequally distributed: that the land is of varying extent and elevation--here a vast plain, far removed from the ocean, and there a mountain chain, interposing a barrier to the free course of the atmospheric currents; sometimes penetrating in full width into the frigid zone, and again dwindling to a few miles under the equator. One very important distinction is also to be remarked, in the superficial area of the different zones, reckoning from the equator, and taking the hemisphere as 100 parts:

Frigid zone 8 parts.

Temperate " 52 "

Torrid " 40 "

For as the time of rotation in every lat.i.tude is the same, the area to be disturbed in the same time, is less in high lat.i.tudes, and there a greater similarity will obtain, _ceteris paribus_. In lower lat.i.tudes, where both land and water stretch away for thousands of miles, it is not wonderful that great differences should exist in the electrical and hygrometric state of the air.

The summer of many countries is always dry--California for instance. In winter, in the same country, the rains are apparently incessant. This of course depends on the power of the sun, in diverting the great annual currents of the atmosphere. As long as the dry north-west trade sets down the coast of California, the circ.u.mstances are not favorable for giving full development to the action of the vortices. When the trade wind ceases, and the prevailing winds come from the south, loaded with vapor, the vortices produce storms of any magnitude; but (and we speak from two years' observation) the pa.s.sages of the vortices are as distinctly marked there in winter time, as they are in the eastern States; and in summer time, also, they are very perceptible. The same remark applies to Mediterranean countries, particularly to Syria and Asia Minor; although the author's opportunity for observing lasted only from April to December, during one season. If we are told it never rains on the coast of Peru, or in Upper Egypt, it does not seriously militate against the theory. The cause is local, and the Samiel and the sand storm of the desert, is but another phase of the question, explicable on the same general principles. From the preceding remarks it will be seen, that in order to foretell the character of particular days, a previous knowledge of the weather at that particular place, and for some considerable time, is requisite; and hence the difficulty of laying down general rules, until the theory is more fully understood.

MODIFYING CAUSES.

We now come to the causes which are auxiliary and interfering. It is natural that we should regard the sun as the first and most influential of these causes, as being the source of that variation in the temperature of the globe, which alternately clothes the colder regions in snow and verdure. The heat of the sun undoubtedly causes the ether of the lower atmosphere to ascend, not by diminution of its specific gravity; for it has no ponderosity; but precisely by increase of tension, due to increase of motion. This aids the ascensional movement of the air, and therefore, when a vortex is in conjunction with the sun, its action is increased--the greatest effect being produced when the vortex comes to the meridian a little before the sun. This has a tendency to make the period of action to appear dependent on the phases of the moon, which being the most palpable of all the moon's variations, has been naturally regarded by mankind as the true _cause_ of the changes of the weather. Thus Virgil in his Georgics, speaking of the moon's influence and its signs:

"Sin ortu in quarto (Namque is certissimus auctor) Pura, nec obtusis per clum cornibus ibit; Totus et ille dies, et qui nascentur ab illo, Exactum ad mensem, pluvia ventisque carebunt."

Hence, also, in the present day we hear sailors speak of the full and change, or the quartering of the moon, in connection with a gale at sea; thus showing, at least, their faith in the influence of the phenomenon.

Yet it is actually the case, at certain times, that in about lat.i.tude 40 and 41, the storms appear about a week apart.

There is some reason, also, to suspect, that there is a difference of temperature on opposite sides of the sun. As the synodical rotation is nearly identical with the siderent period of the moon, this would require about forty-four years to run its course, so as to bring the phenomena to exact coincidence again. Since these observations were made, it is understood that Sig. Secchi has determined that the equatorial regions of the sun are hotter than his polar regions. It may be owing to this fact, that we have inferred a necessity for a change, whose period is a multiple of the sun's synodical rotation, but it is worthy of examination by those who possess the necessary conveniences.

Another period which must influence the character of different years, depends on the conjunction of the perigee of the lunar orbit with the node. Taking the mean direct motion of the moon's perigee, and the mean retrograde motion of the node, we find that it takes six years and one day nearly from conjunction to conjunction. Now, from the principles laid down, it follows, that when the perigee of the orbit is due north, and the ascending node in Aries, that the vortices of the earth will attain their greatest north lat.i.tude; and when these conditions are reversed, the vortices will reach their highest limit in the lowest lat.i.tude. This will materially affect the temperature of the polar regions. In the following table, we have calculated the times of the conjunctions of the apogee and pole of the orbit, taking the mean motions. It may be convenient to refer to by-and-bye, remembering that when the conjunction takes place due south, the vortices reach the highest, but when due north, the vortices in the northern hemisphere have their lowest upper limit:

CONJUNCTION OF APOGEE AND POLE OF ORBIT.[24]

Year. Month and Day. Longitude.

1804, April 18th, 220 1810, " 17th, 104 1816, " 16th, 348 1822, " 15th, 232 1828, " 14th, 116 1834, " 12th, 360 1840, " 11th, 244 1846, " 10th, 128 1852, " 9th, 12 1858, " 8th, 255 1864, " 7th, 139 1870, " 6th, 23 1876, " 5th, 267

By this we see that the vortices have never attained their highest limit during the present century, but that in 1858 their range will be in a tolerable high lat.i.tude, and still higher in 1876--neglecting the eccentricity of the orbit.

A very potent influence is also due to the heliocentric longitude of the sun, in determining the character of any given year. Let us explain:

The moon's inertia forces the earth from the mechanical centre of the terral system, but is never able to force her clear from the central axis. With the sun it is different. He possesses many satellites (planets). Jupiter alone, from his great ma.s.s and distance, is able to displace the whole body of the sun. If other planets conspire at the same side, the centre of the sun may be displaced a million of miles from the mechanical centre of the solar system. Considering this centre, therefore, as the centre of an imaginary sun, from which heliocentric longitudes are reckoned, the longitude of the real sun will vary with the positions of the great planets of the system. Now, although this _systematic_ longitude will not be exactly similar to the heliocentric longitude reckoned from the sun's centre, yet, for the purposes intended, it will correspond sufficiently, and we shall speak of the longitude of the sun as if we reckoned heliocentric longitudes from the mechanical centre of the system. When we come to consider the solar spots, we shall enter into this more fully. In the following diagram we shall be able to perceive a cause for variation of seasons in a given year, as well as for the general character of that year.

[Ill.u.s.tration: Fig. 21]

Let S represent the centre of the sun, and the circle a vertical section of the sun, cutting; through the centre,--SJ being in the equatorial plane of the vortex, of which ZZ' represents the axis. As the ether descends the poles or axis at Z, it is met by the current down the opposite pole, and is thence deflected in radii along the equatorial plane to J. But on the side S, the ether is opposed by the body of the sun; its direction is consequently changed, and cross currents are produced, a.s.suming it as a principle, that the ethereal fluid is permeable by other currents of similar matter, and that it tends always to move in right lines. This granted, it is evident that, in pa.s.sing the sun, the quick moving ether forms a conical sh.e.l.l, (the sun being at the apex,) so that the strongest current of ether is in this conical sh.e.l.l, or at the surface of this conical s.p.a.ce. As the plane of the ecliptic is not much inclined to the sun's equator, and this last probably not much inclined to the plane of the vortex, should the earth have the same _heliocentric_ longitude at the time, (or nearly the same,) she would be in an eddy, as respects the radial stream, and be protected from its full force by the body of the sun.

Now, the ether comes down the axis with the temperature of s.p.a.ce, and may possibly derive a _little_ additional temperature in pa.s.sing over the body of the sun; so that in this position the earth is protected from the chilling influence of the radial stream, by being protected by the body of the sun. And although, from the immense velocity of the ether, it cannot derive much additional temperature, there may still be an appreciable difference, due to this cause.

It is the chilling influence of the ethereal stream which originated the idea among philosophers, of _frigorific impressions, darted from a clear sky_. In some years the sun will be nearly in the centre of the system; in other years the axis of the vortex will not come near the sun. And as the sun's longitude may vary through the entire circle, it may happen that the earth's longitude shall coincide in winter or summer, or spring or autumn. When, however, the earth emerges from the protection of the sun, and enters the conical sh.e.l.l, considered as a s.p.a.ce of considerable depth, she will again be exposed to the full force of the radial stream, rendered more active by the previous deflection, and by the numerous cross currents pervading it; so that a mild and calm winter may be succeeded by a cold and stormy spring. The present season, (1853) the earth's longitude coincided with the sun's longitude in about 135, and consequently was in the conical s.p.a.ce spoken of, during February and March; but the radius vector of the sun's centre, being then less than 300,000 miles, the protection was not as complete as it is sometimes. Still, the general fineness of these months was remarkable; yet in April and May, when the earth became again exposed to the action of the solar stream, the effect was to r.e.t.a.r.d the spring, and disappoint the prognostications of the weather-wise. In applying these principles, we must consider the effect in those lat.i.tudes which are more readily affected,--that is, in the temperate zone, midway between the two extreme zones of heat and cold.

In 1837 and 1838, the longitude of the sun's centre corresponded with the earth's, in August and September, when there was neither rain nor electrical excitement; and consequently those seasons were sickly over the whole country. Now, there is another cause which renders the months of August, September, and October, deficient in electrical energy, and consequently more p.r.o.ne to be sickly. If, therefore, the two causes unite their influence, the autumnal months will be more sickly at those times. This last cause, however, only affects the _northern lat.i.tudes_ in autumn, and consequently, _ceteris paribus_, the autumnal months should not be so proverbially sickly in the southern hemisphere. This is, however, only suggestive.

Again, in 1843, the winter was very mild in January and February; but in March it turned cold and stormy, and continued through April. In this year the longitude of the sun was nearly the same as in 1853,--the two longitudes of the earth and sun corresponding about the last of January; but in March, the earth forsook the comparative calm produced by the sun's position, and hence the greater cold.[25]

Thus it appears at every step we take, that the different members of the solar system do indeed belong to the same family, whose least motions have their influence on the rest. Who could have antic.i.p.ated that the position of Jupiter in his...o...b..t had anything to do with the health of this remote planet, or with the mildness of its seasons? In this we have a clue to the origin of that astrological jargon about planetary aspects being propitious or malign. Philosophers are even yet too p.r.o.ne to wrap themselves in their mantle of academic lore, and despise the knowledge of the ancients, while there is reason to believe that the world once possessed a true insight into the structure of the solar system. As war became the occupation of mankind, under the despotic rule of ambition, so truth retired, and ignorance seizing upon her treasures, has so mutilated and defaced them, that their original beauty no longer appears. Let us hope that the dawn of a better day is approaching.

There is yet another cause (just alluded to) which modifies the action of the vortices.

We have shown that, if the periodic times of the planets are approximately equal to the periodic times of the contiguous parts of the solar vortex, the density of the ether is directly as the square roots of the distances from the centre. As the earth is at her perihelion about the first of January, the density of the surrounding ether is then less than in other parts of the orbit; consequently, if we suppose that there is a continual tendency to equilibrium, the ether of s.p.a.ce must press inwards, during the time between the perihelion and aphelion, (_i.e._ from January to July,) lowering the temperature and increasing the electrical action of those months. As the distance from the sun is most rapidly augmenting about the first of April, and the effective power of the sun's radiation is most rapidly increasing in May; by combining the two we shall find, that about the first of May we shall have considerable electrical action, and cold weather. This explains also, in part, the prevalent tradition of certain days in May being very cold.[26] When the earth leaves the aphelion, a reaction takes place, being most rapid in September. There is then an _escape_ of ether from the earth, which keeps up the temperature, and causes these months to be sickly, from the negative electrical state of the atmosphere. In the southern hemisphere, the effects in the same season will be reversed, which may partly account for the greater degree of cold in that hemisphere, and for accelerating the approach of both summer and winter, while in the north they were both r.e.t.a.r.ded.

We must now advert to another cause, which of all others is probably the most important, at least to the other members of the solar system.

In every part of the solar vortex the ether is continually pressing outwards. We are not now speaking of the radial stream, but of the slower spiral motion of the ether around the axis of the vortex, whose centrifugal force is bearing the whole body of the ether outwards, thus rarefying the central parts, and thus giving rise to the polar influx, from which arises the radial stream. This may be made more intelligible, by reflecting that the polar current is comparatively dense ether, and that the length of the axis of the vortex prevents this influx current coming in sufficient quant.i.ties to restore an equilibrium in the density of the medium. Yet, what does come down the poles, is distributed rapidly along the equatorial plane, leaving the s.p.a.ce still rarefied.

Now we perceive, that in order for the radial stream to continue in action, requires the whole medium of the vortex to be also moving outward; it is therefore continually condensed as it proceeds. This condensation necessarily converts much of the specific heat of the ether into sensible heat; so that the _temperature_ of the medium is continually increasing, as the distance from the sun increases.

When we contemplate the solar system as the emanation of one Great Mind, we naturally seek for evidence of the wisdom of a supreme intelligence in _all_ the arrangements of that system. But, however humbly and reverently we may speak of these arrangements, we can scarcely avoid the wish, that the planetary distances had been differently arranged, if Newton's doctrine be true, that s.p.a.ce is a vacuum, and that the heat of a planet, is inversely as the squares of the distances from the sun.

For, to speak of the temperature of s.p.a.ce, except as dependent on this law, is one of those many incomprehensible inconsistencies with which philosophers are chargeable. If the Newtonian philosophy is literally true, s.p.a.ce has _no temperature_, and the surface heat of the planet Neptune is nearly 1,000 times less than on our own globe. Again, on Mercury it is seven times greater, which heat would scorch and consume every organic substance on the earth, and speedily envelope the boiling ocean in a shroud of impermeable vapor. Granting even that s.p.a.ce may not be a vacuum, and yet the law of gravitation be true, we may still be allowed to consider both Saturn and Ura.n.u.s and Neptune, as inhospitable abodes for intelligent creatures; and, seeing the immensity of room in the system, there is no reason why these planets might not have been permitted to revolve nearer the great source of light and life and cheering emanations. To suggest the resources of Omnipotence is no argument. He has surrounded us with a.n.a.logies which are seen, by which we may attain a knowledge of those which are not seen; and we have every reason to suppose that the great Author of nature is not indifferent to the aspects under which his works reveal him unto his creatures. Yet there is (on the above hypothesis) an apparent want of harmony in the planetary distances; and if frail mortality may be permitted to speak out, an explanation is needed to obviate this seeming anomaly in the economy of the world. The more we learn of the physical arrangements of the universe, the more do they correspond with our experience of the nice adaptation of the means to the end which obtains in our own globe, and we can only judge of other planets by the a.n.a.logies around us. Here, there, are extremes of temperature it is true: it is necessary there should be, and we can see and understand the necessity in all such cases, and how they conduce to the general average of good. But, astronomers can give no reason why it is necessary that some planets of our system should be placed so remote that the sun is frittered down to a star, whose heatless light is but a mockery to those frigid realms.

Now, according to this theory, the temperature of Neptune may be far more uniform and conducive to life than that of our own globe. The chilling influence of the solar stream at that planet being nearly null, and the temperature of the surrounding s.p.a.ce far greater. So also Mercury, instead of being the burning planet of the schools, may suffer the most from cold.

The planet Mars is generally considered, of all the members of the system, most nearly to resemble our own world. The telescope not only reveals seas and continents, but the snowy circles round his poles, which appear to increase and diminish, as his winter is beginning or ending. This planet's ecliptic is similar to our own in inclination or obliquity, his distance, also, is far greater, and his winter longer; yet, for all this, his snow zones are less than on our own globe. This anomalous fact has, we believe, never been noticed before; but it is explicable on the theory, and therefore confirms it. Mars has no satellite, and therefore his centre will be coincident with the centre of the marsial vortex. There will be no _lateral vortices_ to derange his atmosphere, and if the axis of his vortex coincides also with the axis of the planet, the central vortex will be continually over the poles, _and there will be no storms on the planet Mars_. A capital fact connected with this, is the want of belts, as in Jupiter and Saturn; for these planets have satellites, and if _they_ are not ma.s.sive enough, the belts may be produced by an obliquity in the axis of the Jovial and Saturnial vortices. If Mars had an aurora like the earth, it is fair to presume the telescope would ere this have shown it. He is, therefore, in equilibrium. In applying this reasoning to the earth, we perceive that a certain influence is due to the difference of temperature of the ethereal medium surrounding the earth, at perihelion and aphelion, being least at the former, and greatest at the latter.

As a modifying and interfering cause in the action of the vortices, we must mention the great natural currents of the atmosphere, due to the earth's rotation.