[Macmillan's Magazine.

AMONGST the many surprising discoveries which have of late years rewarded the labors of astronomers, none perhaps are more remarkable than those which relate to the phenomena-once thought so in significant-presented by "falling stars.' Ten years ago, though the thoughtful astronomer had become convinced that these objects really belong to the domain of astronomy, doubt still rested on that theory of their nature. Men could scarcely believe that the vast depths amidst which the planets pursue their career around the Sun are the home of countless bodies which rush with even more than planetary velocity upon wide orbits round the solar orb. It seemed incredible that each of those faintly gleaming lights, passing with silent swoop across a stargroup-leaving no trace of their existence and seemingly as little important in the

economy of nature as a rain-drop or a snow-flake-indicates the close of a career during which the mighty orbits of Jupiter and Saturn have been encircled, nay, often the utmost limits of the known planetary scheme overpassed by uncounted millions of miles.

Even now, when the nature of these objects has been revealed to us, and some insight afforded us into the part which they perform in the economy of nature, it seems difficult to realize the full significance of ascertained facts. The very aspect of the planetary scheme seems changed as we contemplate the results of recent labors

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meteoric astronomy. Kepler and Copernicus, could they revisit this world, and, mixing as of old among astronomers, inform themselves respecting the theories now upheld, would scarcely recognize the scheme of the universe so unfolded to their

view. Truly the harmony of the planetary system recognized by Kepler seems strangely marred, as sweet bells jangled out of tune and harsh' by these eccentric meteor orbits. These crowds of independent orbs, rushing disorderly around the Sun, in no sort resemble the obedient family,' which Copernicus recognized in the solar system.

Many times during the last few years the history of those discoveries and researches by which meteoric astronomy has reached its present position has been recounted. It is not my purpose to describe these matters anew. But it has seemed to me that the approach of the Earth towards that great stream of meteors to which the November shower is due, will render a brief discussion of some of the most striking facts lately discovered not unacceptable even to many who look on astronomy from afar off, and regard astronomers somewhat as Indians regard their medicine-men.

We may take the November shootingstars as typical of a class of meteor-systems, which must undoubtedly be very numerous. It is true that as the Earth sweeps on her wide orbit round the Sun she encounters few such streams as that to which the November meteors belong. As she reaches certain critical parts of that orbit she is exposed, indeed, year after year, to a species of cannonade of greater or less intensity; and occasionally the weight of metal with which she is thus assaulted is far heavier than any which she has to encounter during the second week in November. But for a systematic and continuous downpour of missiles the November stream is unsurpassed by any, except perhaps the August meteor-system. If we could count the total number of meteors which have been rained upon the Earth during the past five or six centuries, and assign each individual meteor to its proper system, I have very little doubt that the November stream would be found to have supplied a full tenth part, though the total number of systems which our Earth encounters is known to exceed one hundred.

This being the case, it may be worth inquiring whether the November system is in reality richer than the others-whether there is anything in what we know about this stream to lead us to suppose that it is more important than the rest.

It may be that if

It seems to me abundantly clear that the contrary is the case. We have only two means of judging of the richness and importance of a meteor-system. One is the observation of its apparent richness, and the individual magnitude of the meteors belonging to it. But the apparent richness alone can be but a deceptive indication of the real richness of a stream of meteors. If we were sure that the Earth plunged through the heart of each meteorstream, we could indeed learn something in this way, precisely as we might compare the relative thicknesses of different cords by the resistance experienced in piercing them through the middle with a needle. But we have no assurance whatever that the Earth passes through the heart of a single meteor-system. she did the results would not be altogether pleasing or satisfactory to her inhabitants, and certainly the chances are enormously against her doing so. The minuteness of the space actually passed through by the Earth on her course round the Sun-at least the minuteness of this space by comparison with the dimensions of the solar system-is not commonly appreciated. If we represent the sun as a globe about as large as a billiard-ball, the space along which the Earth pursues her course would be represented by a thread or twine forming a circle nearly eight yards in diameter. Now conceiving such a circle, and regarding the meteor-systems as oval hoops round the central ball, which happen to cross this fine circular thread, it is scarcely conceivable that in one case out of a thousand the thread would pass centrally through the substance of one of the hoops.

We can therefore infer little or nothing from the apparent richness of meteorstreams as to their real importance, because we do not know whether our Earth passes through the core of any particular stream or merely grazes its surface.

We may learn something from the average dimensions of the meteors belonging to a system, though our inferences may not be altogether reliable. So far as this point is concerned, the November meteors would seem relatively inferior to many others. They are too small to penetrate through the atmosphere, so as to reach the surface of the Earth, not one instance being on record of a November meteor affording any tangible evidence of its existence; and from the researches of

Professor Alexander Herschel, it would seem that on the average the November meteors weigh but a few grains each. When we compare this with the fact that bodies belonging to other systems have been found to weigh many pounds, some even being several tons in weight, the relative insignificance of the November system in this respect will be clearly recognized.

But there is a second method by which in comparatively recent times it has become possible to guess at the importance of different meteor-systems.

The surprising discovery that many meteor-systems are associated with comets has not hitherto been fully interpreted. We know quite certainly that along the orbits of certain comets there there travel myriads of tiny bodies-meteors-which we assume to be solid. But what connection there may be between the gaseous comet and its solid attendants, whether the comet gave birth to the meteors, or whether the meteors in some way or other combined along one part of the system to form the comet, has not hitherto been explained. It may be regarded indeed as one of the most mysterious facts ever discovered by astronomers that any association whatever should exist between bodies seemingly so different in their nature as comets and meteors. But there the relation is, let us make of it what we will. No doubt rests on the reality of the discovery; no one who understands the nature of the evidence can believe for a moment that the relationship is merely apparent, and the coincidence of orbits merely accidental. So that, in fact, it has come to be gravely questioned whether any meteor-system exists without cometic nucleus, and whether any comet exists without a meteoric train.

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Be this, however, as it may, we are at least justified in comparing together such meteor-systems as are known to be associated with comets, and inferring the probable importance of such meteorsystems from the observed brilliancy of their comet-chief.

Now, judging in this way, we should be led to conclude that the November stream, notwithstanding the wonderful magnificence of the star-showers observed when the Earth passes through the system, is in reality one of the least important of the meteor-systems. The comet with which

it has been (beyond all question) associated, is so faint and small that it has never yet been discerned by the unaided eye. In a powerful telescope it appears but as a faint nebulous light, nor is it even adorned with the ordinary appendage of respectable comets-a tail. Taken apart from the significance of what we know respecting it, this comet is certainly one of the least striking objects which the telescope has ever revealed to astronomers.

On the other hand, the August meteors are associated with a comet of distinction -with a comet which has been watched by many millions of human beings as the harbinger of some uncanny event, and has been recognized even by men of science as worthy of respectful attention. Indeed, if its approach had been anticipated and its course known, but the hour of its arrival uncertain, it is far from unlikely that men of science would have looked forward with some dread to the possible effects of its arrival. For it was one of those comets-few, indeed among the larger sort-whose track crosses the Earth's; and had it come but a few months earlier or later, we should by this time have had the means of answering that long-vexed question whether the Earth would suffer injury were she to come into direct collision with a large comet. So that if we judged of the relative importance of the August and November meteorsystems by a reference to the relative importance of their comet companions, we should undoubtedly conclude that the August meteors are far the most important. It would follow from this that, since the November meteor-system produces showers quite as striking as any seen in August, we do not in reality see the full splendor of the August meteors, but, passing only through its edge, recognize but the scattered outliers of the system.

But this being so, those who remember the magnificent display of November metors in 1866, will consider with amazement how grand the August system must be if it is really capable of supplying a far more splendid shower. We remember how the stars seemed to fall continuously, so that at every instant (at least during a certain interval) shooting-stars could be seen in some part or other of the heavens. And we know, also, from the accounts of Humboldt and Bonpland that, sixty years before, there had been a yet grander dis

play. If a meteor-system associated with so insignificant a comet as that of 1866 can produce these wonderful showers, how inconceivably magnificent would be the scene if the Earth passed through the heart of the August meteor-system, associated as that system is with a comet of considerable splendor!

But similar considerations may fairly be extended to all the meteor-systems which the Earth encounters. These are counted by the hundred, and though most of them seem insignificant compared with the August and November systems, yet we have seen that no opinion can hence be formed of their real importance. Some of them may as far exceed the August system in importance as that system probably exceeds the November system. Nay, we have two excellent reasons for feeling some degree of assurance in this respect; for one of these less noted systems has been associated with the comet of 1861-an object not inferior in splendor to Donati's comet-and some of the recognized systems occasionally sent us visitors in the form of massive aërolites, compared with which the tiny bodies forming the August and November meteors are as small shot to the Whitworth bolts. Startling, however, as are the considerations thus suggested, it is when we pass in imagination beyond the confines of the Earth's orbit that the true significance of what we know respecting meteors and meteor-systems becomes apparent.

We have seen that our Earth really visits but a minute proportion of the solar domain. The space actually traversed by our globe as it circuits round the Sun, though enormous compared with any of our ordinary estimates of size-nay, though exceeding fiftyfold the volume of the Sun —is yet but the minutest fraction of that vast sphere over which the Sun exerts

supreme sway.

Now, since the meteors are not individually discernible save when they enter the Earth's atmosphere, all our direct information respecting the condition of the interplanetary spaces is derived from the actual contact of the Earth with bodies belonging to those spaces. We obtain our information respecting the planets through their visibility, but as respects the meteors our Earth may be compared to a blind man in a shower. It is only when the meteors or meteor-systems come into NEW SERIES.-VOL. XVI., No. 5

actual contact with her that her inhabitants can have direct cognizance of the existence of such bodies. Let us follow out this illustration. Suppose a blind man walked a distance of ten miles, and during the whole continuance of his walk felt rain falling upon him. Would it be a reasonable conclusion on his part that the rain had fallen precisely along the track he had followed, and nowhere else? Would he not conclude, on the contrary, that the extent of country on which the shower had fallen extended probably, at least, as far from right to left as he had found it to extend in the direction of his walk? Most assuredly he would not conclude that a narrow strip, ten miles long and perhaps a yard wide, had been rained upon, but rather an area several miles wide. In other words, he would conclude that, instead of an area of a mere fraction of a mile in extent, a range of forty or fifty square miles, at least, had been visited by the shower.

It is equally reasonable to conclude that the track of the Earth is not the only part of the Sun's domain which is crossed by meteor-systems. There is no conceivable reason why that particular hoop of space should be visited rather than regions lying around it. And precisely as our illustrative blind man, had he stepped to the right or to the left of his actual path, would have been visited by other rain-drops than those which actually fell upon him, so we may reasonably conclude that if our Earth's orbit were changed so that she travelled a few millions of miles further from or nearer to the Sun than she actually does, then she would encounter meteorsystems altogether different from those which now assail her with a shower of 'pocket planets.' To come to the point for which I have been making all along,— the whole of the solar domain is alive with meteors. This is the legitimate conclusion from the evidence acquired during the last few years. So long as it was thought that the meteor-systems are nearly circular, there was an escape from this startling conclusion. It was conceivable that the meteor-systems might affect the neighborhood of the Earth's orbit, much as the asteroidal family affects the space lying between the orbits of Mars and Jupiter. But so soon as Adams and Leverrier, Schiaparelli, Tempel, and the rest, had made it abundantly evident that the me

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teors travel in very eccentric orbits, there remained no escape from the conclusion that the intersection of these orbits with the Earth's path is to be regarded as a merely accidental circumstance. The Earth has absolutely no power adequate to force these meteor-systems to cross her orbit. We could undertand the orbit of Jupiter or Saturn being crossed by many meteor-systems, because we know that if a family of meteors were passing close by Jupiter on a course which would carry the family far away again into space, the mighty attractive force of Jupiter or Saturn would (ordinarily) suffice to force the members of that meteor family to come close to the planet before they could speed again on their course towards the Sun's neighborhood. Whenever such an encounter as this took place, the meteor family would, for the future (and until again disturbed by the planet), travel on a path crossing or very closely approaching the planet's. But the Earth is far too small to influence in this way the motions of meteoric families. Those which approach her speed onwards with a velocity altogether beyond her control, so that, unless already travelling on a re-entering orbit passing close by the Earth's, they could never be forced by her attraction to enter on such a track. A body coming from the stellar depths towards the Sun could no more be forced by the Earth's disturbing attraction to follow a closed curve round the Sun, than a swiftly-rushing railway train could be caused to leave the rails by the attraction of a toy magnet.

Since, then, those meteor-systems which cross the Earth's orbit are chance visitors, as it were, not drawn to their present paths by any attraction the Earth can exert, but coming of their own accord past her track, it follows that there must be for each recognized meteor-system uncounted thousands which are unknown to us because they do not approach the Earth's track. There is no escape from this conclusion. The laws of probability will not permit us to believe that, out of a moderately large number of meteor-systems in no way attracted to the Earth's orbit, a large proportion would traverse that particular track in space. To judge the number of meteor-systems as no greater than the number encountered by the Earth, would be like counting the raindrops which fall upon a window-pane in

London, and concluding that just that number and no more had fallen on the whole city.

It is this conclusion which gives so great an interest to the researches of Adams, Leverrier, and others on the November meteor-system. If we were sure that that meteor-system was the only one of its kind, or had but few fellows, we could attach no great importance to its peculiarities. They would have a certain interest, doubtless, precisely as the discovery of an asteroid has a certain interest; but they would involve no results of cosmical significance. Under the actual circumstances, what has been proved respecting the November meteors opens a field of conjecture of almost boundless extent. Whence come these uncounted millions of bodies, rushing through space with inconceivable velocity? What purpose do they fulfil in the economy of the solar system? Do any of them pour upon the Sun, as has been supposed, a hail of cosmical material, replenishing his fires and recuiting his energies? Has the mighty attractive influence of the Sun, which guides the planets on their wide circuits, this further work to perform, of gathering from out of space the material by which his own fires are fed? Or do these myriads on myriads of cosmical bodies, with all the vital forces represented by their velocity, subserve no purpose whatever in the economy of our system? Are they the chips in the great workshop .of Nature, the sparks which have flown from the mighty grind-stone, the shreds of clay which the giant potters Attraction and Repulsion have cast aside as useless ?

This paper was accompanied by the following note:

Our readers may be desirous of learning what are the chances that the display of November meteors will this year be worth observing. In 1866, it will be remembered, the great display lasted but a few hours. Had it occurred either a few hours sooner or a few hours later, we, in England, should not have witnessed it. In the former case we should have been on the sheltered part of the Earth—to leeward, so to speak, of the meteor storm; in the latter, though the meteors would have fallen upon portions of the atmosphere above our horizon, it would have been full