of the prophets. In cases of planetary attraction, the earth's crust becomes attracted as a solid whole. Its fluid and aerial envelope responds when irregularly attracted, by oscillating in high and low tides, alternating with unequal pressure. We are approaching both stellar and planetary conditions which fortunately will require a certain number of years say 1880 to 1885-for their complete unfoldment ; hence their action may not be wholly manifest in a special month of any year; but this whole cycle of years is liable to be affected by a generally disturbed condition of the earth and its inhabitants.'

But utter rubbish as all this is-the offspring of sheer ignorance and hysteric vapours-it is not much more absurd than the prediction recently based on the observed fact that the comet of 1880 travelled along the same path as that of 1843, this path lying very close indeed to the sun. Assuming, as is really not improbable, that the comet of 1843 passed so near to the sun as to have been retarded by the resistance of the corona, and so came back after a shorter circuit than it had before traversed, it is likely enough that the comet will next return after a yet shorter interval. Possibly Marth's period-' say seventeen years,' he puts it— may be nearer the truth, in which case the comet would come back in 1897. The next return after that might be in seven or eight years, say in 1904. The next perhaps is three or four, and very likely by about the year 1920 or 1925 that comet may reach the end of its career, being finally absorbed by the sun. It is also very likely that if, instead of being thus gradually checked off, so to speak, this comet in its original full-sized condition, with many millions of millions of meteoric attendants, had rushed full tilt upon the sun, it might have done a deal of mischief. very able astronomer, Professor Kirkwood, of Bloomington, Indiana, believes (and very likely he is right) that two of the larger meteoric attendants on this comet falling into the sun in September 1859, produced that remarkable solar disturbance which was accompanied by very remarkable mag

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netic disturbances and auroral displays all over the earth : so that doubtless the whole comet with its attendants pouring all at once upon the sun would have stirred him in a way which we should have found very noteworthy, even if we did not find it absolutely destructive to the earth and its inhabitants. But as a mere matter of fact (and so counting for something, whatever end-of-the-world prophets may imagine) the comet of 1843 and 1880 does not travel full tilt upon the sun, and can never do so; its meteoric attendants are not all gathered in a single cluster, but form an immensely long train (if Kirkwood was right in the above quoted surmise, those which fell into the sun in 1859 were at least sixteen years behind the main body); and it is clear that a very effective interruption of the comet's career in 1843, repeated in 1880, can take place without in any appreciable degree affecting our comfort, still less our existence. If the comet of 1880 was the same object as the object of 1843, it showed very evident signs of having suffered grievously during its former perihelion passage. If it is proportionately reduced at its next return, we might even see it fall straight upon the sun (were that possible) without much fearing any evil consequences. Nothing which is known about comets in general, or about this comet in particular, suggests the slightest danger to the solar system, though everything suggests that the comet's career as an independent body will before very long come to an end. If the comet ever was a dangerous one, owing to the concentration of its meteoric components, it is not so now. If it really has been effectively checked in its career, it is evident such interruption can take place without harming us, and therefore the final throes of the comet need not trouble us in the least. If it has not been effectively interrupted, then the end is not nearer in any appreciable degree-now than it was in 1843 or in 1668. In any case, the end of this comet's career, whether far off or near at hand, will in all probability take place in such a way that terrestrial astronomers will never know of the event.

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THE MENACING COMET.

IN 1881 a dismal report appeared, to the effect that the comet of 1843, which was supposed to have returned in 1880, would come back again in 1895 and bring about the end of the world. The origin of the report was not altogether clear. At least it was not altogether clear to the writer of these lines, who, if the report had had any legitimate foundation, should have known something about it. It seems that a remark to the effect that the comet of 1880 travelled in the same orbit as the comet of 1843, and was probably the same body, but that if that were the case, it had returned long before it should have done, so that the period of revolution seemed to be shortening, had been to some degree misapprehended.

It had been suggested by several Fellows of the Royal Astronomical Society that if the comet of 1880 were really the same as that of 1843, the next return might occur in a very few years; perhaps, said Mr. Marth, in about fifteen; and each return thereafter at shorter and ever shorter intervals. For the path of the comet carries it in very close proximity to the orb of the sun; and it is generally believed that a retardation of the comet's motion must occur at each return to the sun's neighbourhood, for the simple reason that the comet can hardly be supposed to get through the matter which forms the sun's corona, without encountering some resistance. The more the comet is retarded by such resistance, the faster it will travel round its orbit-paradoxical though this may sound. At each return it will encounter

more and more effective resistance, until at length it must be absorbed into the body of the sun.

Whether such absorption would produce any great effect or not upon the sun, and through him upon the solar system, was a question which to many seemed answerable only in one way. Newton had pointed out that comets might serve as fuel to the sun, and perhaps produce disastrous effects in that way, by unduly increasing the solar light and heat. comet,' he said, 'after certain revolutions, by coming nearer and nearer to the sun, would have all its volatile parts condensed, and become a matter fit to recruit and replenish the sun (which must waste by the constant light and heat it emits) as a faggot would this fire if put into it.' (He was speaking to Mr. Conduitt at the time, beside a wood fire.) 'And that would probably be the effect of the comet of 1680 sooner or later; for by the observations made upon it, it seemed to have a tail of thirty or forty degrees, when it went from the sun. It might, perhaps, make five or six revolutions more first; but whenever it did, it would so much increase the heat of the sun, that this earth would be burnt, and no animals in it could live.' 'He took the three phenomena seen by Hipparchus, Tycho Brahé, and Kepler's disciples,' he added, 'to have been of this kind; for he could not otherwise account for an extraordinary light, as those were, appearing all at once amongst the fixed stars (all which he took to be suns enlightening other planets, as our sun does ours) as big as Mercury or Venus seems to us, and gradually diminishing for sixteen months and then sinking into nothing.'

But although what we now know respecting the mass of comets is by no means so much opposed to these views as many seem to imagine, our knowledge of the way in which the sun's heat is maintained will not permit us to adopt Newton's opinion. Nor will the accepted views as to the origin of the sun's heat justify us in accepting a belief in more than a very moderate accession of heat as likely to accrue, under any influences due to comets now actually

All those which have passed

travelling around the sun. once round the sun's immediate neighbourhood, can pass again, and yet again, with effects which can never greatly exceed those produced at their first passage. If at any one perihelion passage a comet is slightly retarded, it will be slightly retarded again at its next passage close by the sun, somewhat more at the next return, and so on continually, until it is finally absorbed, the interval between these passages continually diminishing. Only in the case of great retardation at one passage, will the retardation at the next perihelion passage be markedly greater; but in this case the effects at the earlier passage should have been noteworthy; so that as no noteworthy sudden accession of solar light and heat has ever been observed, no such earlier passage has yet occurred which should make us seriously fear the next passage of the same comet by the sun's neighbourhood.

The fears entertained, therefore, respecting the next return of the comet of 1843 are without foundation. If that comet was really so checked in speed in 1843 that it returned in thirty-seven years instead of the much longer period assigned to it by the best astronomers, then we had an opportunity at that time of estimating the effect of such interruption of the comet's motion. But no effects were then perceived. The sun was neither brighter nor hotter than usual. The inference is, then, that that frictional resistance cannot appreciably affect the sun's condition. In 1880 we had a repetition of this experience-assuming that the comet of 1880 was the same body. The sun in 1880 shone much as he had done in 1879, much as he did later in 1881 and 1882. So that the world might await with calmness the future returns of this sunlashing comet, satisfied that whatever effect might be produced on the comet, very little would be produced on the sun or the solar system.

But now suddenly news comes that a comet has been seen which American men of science have identified with the comet of 1843 and 1880, so that from thirty-seven years