THE STORY OF THE COMETS.* MR. CHAMBERS'S book must be

acknowledged to be thoroughly well timed. Whether we view Halley's Comet from the "standpoint of the historian or the astronomer," the author reminds us that it must be regarded as by far the most

• The Story ot1k4 Comet/. By (1. F. Chambers, F.R.A.S. Oxford : at the parencivaines& ple„netha

interesting of all the comets recorded in history. Halley, with whose name the comet has been associated, owing to his prolonged calculations of its orbit, found that it was one with the comets of 1531 and 1607. This was after its reappearance in 1682, which thus gave it a period of somewhere about seventy-five and a half years. Yet Halley was very greatly troubled by certain discrepancies between the known facts and the results of his reasonings ; but finally, by an effort of imagination, tested by prolonged calculation, he discovered that the influence of the planet Jupiter had affected the velocity of the comet, and thus shortened its orbit. He ventured to predict that it would return about the end of 1758, and wrote concerning it the following almost pathetic sentence :—" Wherefore if it should return according to our prediction about the year 1758 impartial posterity will not refuse to acknowledge that this was first discovered by an Englishman." It did return, and was first seen on the night of Christmas Day, 1758, by an astronomically inclined farmer named Palitzsch, living near Dresden. And, as Hind has remarked, posterity has not attempted to deprive Halley of the honours which were his due. Indeed, only this very year it was announced that the Admiralty have decided to repair his tomb at the public expense. The comet was seen on the morning of August 6th, 1835. And now we are expecting it to make its appearance again in our skies. As we write we cannot but ponder how some aged man may look at it with tired eyes,—at the same strange light in the sky which some seventy-five years ago he viewed wonderingly, as a little child. This is a thought that must arise in many a mind when the comet arrives. And away in the ages 250 B.C. it is now certain that this same comet was visiting the earth.

Regarding comets in general Mr. Chambers tells us many things. He remarks gently on the popular fallacy that comets must always have tails, pointing out that the majority of comets are tailless. When first seen, telescopically of course, the ordinary comet shows merely as a faintly luminous speck.

Gradually its size increases, and after a while a nucleus of condensed light appears. The size and brilliancy increase, and presently—if there is going to be a tail-development-

the cloudlike outer mass of the comet becomes less sym-

metrical. Speaking in general terms, it may be said that those comets which make their perihelion passage (i.e., nearest approach to the sun) at a comparatively short distance develop tails, whilst those which make the passage at a great distance do not develop tails, or only rudimentary ones. In the matter of collets and their tails, the author reminds us that the tail is hi nearly every instance pointing from the sun, whether the comet is approaching or receding. To explain this phenomenon, he gives the time-worn and somewhat vague semi-explanation of the sun's being supposed to send out a repelling force.

Speaking with "great reserve," Mr. Chambers says that comets "are made of" probably a mixture of solid and gaseous matter. The sizes of the solid particles are, of course, unknown. Many suggestions have been made, such as paving- stones, brickbats, and, again, grains of sand. With regard to colour, he says that most comets "exhibit a more or less silvery-grey hue." He admits to being sceptical as to the correctness of the "sensational assertions of many ancient and mediaeval writers of comets appearing of the colour of blood, or fiery red." At the same time, he admits that "we do find in the writings of modern astronomers sufficient evidence

to show that such tinges as yellowish,' or yellow,' or 'ruddy' are not unprecedented. both as regards nuclei and

tails." The author gives some interesting details of the comet

of 1680, and its emotional-religious effect. So great was the terror inspired by this celestial visitor that in Germany, to allay the general fear, a special medal was struck, having a picture of the comet, with the dates, on one side, and on the other the following inscription :— " The star threatens evil things; Only Trust! God will make things turn to good."

This comet also inspired the Rev. William Whiston to write his extraordinary New Theory of the Earth, in which he sought to prove that the Deluge must be ascribed to one of the visits of this very comet.

In the chapter on "Remarkable Comets" the author gives again the famous details of the Great Comet of 1861, through the tail of which it is supposed the earth may have passed

early on June 30th. On the ,evening of that day it was remarked by many observers that the sky had an extra- ordinary appearance : "a peculiar phosphorescence or illumina- tion of the sky an auroral, glare-like look." But Mr.

Chambers does not speculate much on the imaginative side of his subject ; so that startling suggestions and impressive- sounding facts are for the most part conspicuous by their absence. Yet we may be permitted here to observe that a quite incorrect sense of security has been arrived at in the matter of the actual quality of danger with which comets are invested. It is true that the earth may have passed through

the unknowably sublimated ethereal dust of light of the comet's tail, and that no contamination of the atmosphere was apparent ; but it is futile and absurd to quote this fact, as is so generally done, to uphold the unprovable contention that comets are in no ways a source of danger to the Planet Terra. We can conceive of a nearer acquaintance with the nucleus of a large comet as holding uncomfortable possibilities. It is interesting to remember that Napoleon is said to have regarded the Great Comet of 1769 as his protecting Ode ; but if, as is sometimes thought, he entertained a similar mania concerning the comet of 1811 in the matter of his successful invasion of Russia, he must have had a painful lesson in the futility of such fancies. And whilst we are dealing with the comets of history and poetry, it is interesting to recall the dis- crimination of Gadbury, "an astrological gentleman," between comets and comets. From him we learn that "an hairy comet denoteth the death of Kings," and that "a comet like a sword portendeth war." It is extraordinary to remember that even as late as 1872 a comet was capable of inspiring such fear that in Atlanta, Georgia, the confessionals were crowded; families kept watch all night in order that "i.f the worst came they might be awake to meet it." The orgies round the " coloured " churches would have been laughable had it not been for the utter and frightened seriousness of the worshippers.

Among the various theories which have grown up con- cerning comets, we notice that Mr. Chambers gives a refutation to that which ascribes to them the power of affecting the temperature. It is true, the author says, that more comets are discovered in hot years than in cold ; but this is for the simple reason that hot years give clear skies, naturally more favourable for the discovery of comets than cold years, which so often mean cloudy skies. He has a quiet little laugh at the methods of certain French astronomers who propound such foolish questions as "Are comets habit- able ?" merely, it would seem, for the pleasure of taking several pages to say "No."

How many elderly men of to-day, we wonder, remember finishing their last bottle of "Comet Wine," which was put down, Mr. Chambers tells us, in the year of the Great Comet, 1811? The last advertisement of this wine appeared in the Times "somewhere in the 'Eighties,' so that the wine and the label thereof lasted long." Speaking of the Great Comet, it is impressive to remember that its tail measured a hundred million miles in length, and that its aphelion distance is about forty thousand million miles and its period over three thousand years. What water will have run under the bridges when next it appears ! In ending this brief account of an exhaustive book we would remind the reader that it is eminently suited even to those amateur astronomers who have not ceased to believe of all comets that of necessity "thereby hangs a tail."