Part 3

The comet's tail seems, in reality, to be a thin oblong case of vapour, formed out of the cometic substance by the increasing intensity of the sunshine, and enclosing the denser portion of that substance at one end. The diverging streams which it displays upon the sky are merely the retiring edges of the rounded case, where the greatest depth of luminous matter comes into sight. As the comet nears the sun, much of its substance is vaporised for the construction of this envelope; but as it goes off again into remoteness, the vaporous envelope is once more condensed. The tail may then be seen to flow back towards the head, out of which it was originally derived.

But here, again, a difficulty presents itself. The comet's tail is believed by most of the illustrious astronomers of the day, to be the body converted into vapour by solar influence. If it be so, the vaporising process must be a much more subtile one than any that could be performed in our alembics, for the comet's substance is already all vapour before the distillation commences. The faintest stars have been seen shining through the densest parts of comets without the slightest loss of light, although they would have been effectually concealed by a trifling mist extending a few feet from the earth's surface. Most comets appear to have bright centres--nuclei, as they are called; but these nuclei are not solid bodies, for as soon as they are viewed by powerful telescopes, they become as diffused and transparent as the fainter cometic substance. Comets are properly atmospheres without contained spheres; enormous clouds rushing along in space, and bathed with its sunshine, for they have no light excepting sunlight. They become brighter and brighter as they get deeper within the solar glare, and dimmer and paler as they float outwards from the same. The light of the comet only differs from the light of a cloud that is drifted across the cerulean sky of noon, in the fact, that it is reflected from the inside as well as the outside of the vaporous substance. The material illuminated reflects light, and is permeated by light, at once. In this respect it resembles air as much as cloud--the blueness of the sky is the sunlit air seen through the lower and inner strata of itself. In the same way, the whiteness of the comet is sunlit vapour seen through portions of itself. The sunbeams pass as readily through the entire thickness of the cometic substance as they do through our own highly permeable atmosphere.

The belief in the comet's surpassing thinness and lightness is not a mere speculative opinion. It rests upon incontrovertible proof. In 1770, Lexell's Comet passed within six times the moon's distance of the earth, and was considerably retarded in its motion by the terrestrial attraction. If its mass had been of equal amount with the earth's mass, its attraction would have influenced the earth's movement in a like degree in return, and the earth would have been so held back in its orbitual progress in consequence, that the year would have been lengthened to the extent of three hours. The year was not, however, lengthened on that occasion by so much as the least perceptible fraction of a second; hence it can be shewn, that the comet must have been composed of some substance many thousand times lighter than the terrestrial substance. Newton was of opinion, that a few ounces of matter would be sufficient for the construction of the largest comet's tail.

Light as the comet's substance is, it is not, however, light enough to escape the grasp of the sun's gravitating attraction. When the mass of thin vapour is rushing through the obscurity of starlit space, so far from the sun that the solar sphere looks but the brightest of the stellar host, it feels the influence of the solar mass, remote as it is, and is constrained to bend its course towards it. Onwards the thin vapour goes, the sun waxing bigger and bigger with each stage of approach, until at last the little star has become a fiery globe, filling up half the heavens with its vast proportions, and stretching from the horizon to the zenith of the visible concave. The great comet of 1680 came in this way from a region of space where the sun looked but half as wide as the planet Mars in the sky, and where the solar heat was imperceptible, the surrounding temperature being 612 degrees colder than freezing water, into another in which the sun filled up 140 times greater width of the sky than it does with us, and where the heat was some hundred times higher than the temperature of boiling water. It was then only 880,000 miles away from the solar surface, and would have fallen to it in three minutes, in obedience to its attraction, if the impetus of its motion in a different direction had been on the instant destroyed or arrested. But this impetus proved too great for the attraction, light as the material of the moving body was. When the comet has approached comparatively near to the grand source of attraction, the speed of its accelerating motion has become so excessive, that it is able to withstand the augmented solicitation it is subjected to, and move outwards in a more direct course. It goes, however, slower and slower, and curving its journey less and less, until at last its motion in remote obscurity is again so sluggish, that the sun's attraction is once more predominant, and able to recall the truant towards its realms of light. Such is the history of the comet's course.

Thin comet vapours drift through space, sustained by exactly the same influences that uphold dense planetary spheres. They are supported in the void by the combined effects of motion and attraction. Their own impetus strives to carry them one way, while the sun's attraction draws them another, and they are thus constrained to move along paths that are intermediate to the lines of the two impulses. Now, when bodies are driven in this way by two differently acting powers, they must travel along curved lines, if both the driving forces are in continued operation, for a new direction of motion is then impressed on them at each succeeding instant. There are three kinds of curved lines along which bodies thus doubly driven may move: the _circular_ curve, which goes round a central point at an unvarying equal distance, and returns into itself; the _elliptical_ curve, which returns into itself by a route that is drawn out considerably in one direction; and the _hyperbolic_ curve, that never returns into itself at all, but has, on the other hand, a course which sets outwards each way for ever. The _parabolic_ curve, as it is called, is a line partaking of the closeness of the ellipse on the one hand, and the openness of the hyperbola on the other. A parabola is an ellipse passing into a hyperbola; or, in other words, it is a part of an ellipse whose length, compared with its breadth, is too great to be estimated, and is consequently deemed to be endless for all practical purposes.

In most instances, comets move in space, about the sun, in ellipses so very lengthened, that their paths seem to be parabolas as long as the cloudy bodies are visible in the sky. Two of them, Ollier's Comet and Halley's, are known to return into sight after intervals of seventy-four and seventy-six years, during which they have visited portions of space a few hundred millions of miles further than the orbit of Neptune. Six comets travel in elliptical orbits that are never so far from the sun as the planet Neptune, and return into visibility in short periods that never exceed seven or eight years. These interior comets of short period seem to be regular members of our world-system in the strictest sense. Their paths, although more eccentric, are all contained in planes that nearly correspond with the planes of the planetary orbits, and they travel in these paths in the same general direction with their planetary brethren in every case. The planetoid comets of short period are--Encke's, De Vico's, Brorsen's, D'Arrest's, Biela's, and Fage's. The comet of 1843 is half suspected to belong to the group, and to be also a periodic body, revisiting our regions punctually at intervals of twenty-one years.

The comet's motions strikingly illustrate the almost absolute voidness of space. If the thin vapour experienced any resistance while moving, its free passage would be checked, although that resistance was many thousand times less than the one the hand feels when waved in the air. It is found, however, that Encke's Comet does indicate the presence of some such resistance. It goes slower and slower with each return, and contracts the dimensions of its elliptical journey progressively. But it must be remembered, that this is one of the close comets that never gets well out of the solar domain in which our neighbouring planets float. The resisting medium which opposes its journey may be merely an ethereal solar atmosphere surrounding the sun, as our air surrounds the earth, but spreading to distances of millions instead of tens of miles. On the other hand, it must be remembered also that starlight passes through universal space, and is everywhere spread out therein, and that it is hardly possible to think of starlight as an existence without some sort of material reality. Some physicists believe that Encke's Comet, with its retarded motions, will some day fall into the sun; while others fancy that such a consummation can never take place, because successive portions of its substance will be thrown off by the tail-forming process with each perihelion return; so that long before the cometic mass could reach the sun, it will have been altogether dissipated into space, and nothing will be left to accomplish the final state of the fall.

The great peculiarity of cometic paths, as compared with the planetary ones, is, that they consist of ellipses of very much more eccentric proportions; and that, therefore, the bodies moving in them, go alternately to much greater and less distances from the sun than the planets do. It must not be imagined, however, that all comets revolve about the sun even in the most lengthened ellipses. Three at least--the comets of 1723, 1771, and 1818--are known to have moved along hyperbolic paths instead of parabolic or elliptical ones. These comets, therefore, can make but one appearance in our skies. Having once shewn themselves there, and vanished, they are lost to us for ever. They are but stray and chance visitors to the domains of our sun, and refuse to submit themselves, with the more regular members of their fraternity, to the regulation-arrangements of our system, or to appear punctually at the systematic roll-call therein instituted. They are the true free-wanderers of the Infinite, passing from shore to shore of immensity, and presenting themselves, for short and uncertain intervals, to star after star. When they flit through our skies, they shew themselves in all possible positions, and move along all possible directions. They sometimes, however, yield too much to temptation, and have to suffer the penalty of a short imprisonment in consequence. Lexell's Comet, for instance, rushed in its hyperbolic path too near to Jupiter, and was caught in the attraction of its mass, and made to dance attendance on the sun through two successive elliptical revolutions. At the end of the second, the influence that had impounded the comet came, however, into play oppositely, and restored it again to its wandering life and hyperbolic courses. Its cloudy form has not presented itself amongst our stars since 1770, when its visit was thus strangely received by Jupiter.

Twenty-three comets were seen by the naked eye during the sixteenth century, 12 were seen in the seventeenth, 8 in the eighteenth, and 9 in the first half of the nineteenth. This does not, however, give anything like an adequate idea of the number of comets really in existence. When Kepler was asked how many comets he thought there were, he answered: 'As many as there are fishes in the sea.' And modern science seems determined, that the sagacious German shall not be at fault even in this predication. Two or three fresh telescopic comets are now usually found out every year. In 1847, 178 comets were known to be moving in parabolic orbits, and therefore to be in some way permanent connections of our world-system. Lalande has enumerated 700 comets, but Arago believes that not less than 7,000,000 exist, which fall at some time or other within the reach of our sun's influence.

THE SLEEPY LADY.

She is easy, good-natured, and compliant about everything but her sleep. On that point she can bear no interference and no stoppages. Unless she had it fully out every day, neither would life be worth having for herself, nor would she allow the life of any other people to be endurable. Sleep is her great gift; her body has been wonderfully constituted to take a great deal of ease. Deprive her of that, and you starve her as effectually as you famish a human being by abstraction of food. Her personal appearance confirms her philosophy; for you can detect not one particle of restlessness about her. All is soft, rounded, and woolly, as if she carried an atmosphere of deafening about with her.

It has been her habit ever since her earliest years. One of the principal anecdotes of her girlish days now remembered in her family is, that her mamma having sent on some exigency to rouse her, she faintly murmured forth, 'Not for kingdoms!' then turned on the other side, and doggedly went to sleep again. There is another story of her having had to rise one morning at half-past seven, in order to attend a friend as bridemaid, when, coming down stairs, and seeing it to be a raw drizzly day, she pronounced her situation to be 'the ne plus ultra of human misery!' She told the young bride (by way of a compliment) that she would not have got up in _the middle of the night_ to be present at the marriage of any other friend on earth. This phrase might seem to most people only a pleasant hyperbole; but I am not quite sure that it was so intended. The fact is, she has seen so little of the world at any other hours than between noon and midnight, that she has a very obscure sense of other periods of daily time. She scarcely knows what morning is. Sunrise is to her as much of a phenomenon as a total eclipse of the sun to any other person. She cannot tell what mankind in general mean by breakfast-time, for she has scarcely ever seen the world so early. And really half-past seven was not very far from the middle of _her_ night.

Her husband, who is a little of a wag, compares her waking-life to the appearance which the sun makes above the horizon on a winter day: only, her morning is about his noon. He says, however, there appears to be no necessary end to her sleep. It is like Decandolle's idea as to the life of a tree: keep up the required conditions, as sap, &c., and the tree will never decay. So, keep up the necessary conditions for her repose, and she continues to sleep. It is always some external accident of a disturbing nature which gets her up. He has sometimes proposed making an attempt so to arrange matters as to test how long she _would_ sleep. But, unfortunately, he cannot provide against the disturbing effect of hunger, so he fears she might not sleep above two nights and a day at the most--a result that would not be worth the trouble of the experiment. She takes all his jokes in good-humour, as indeed she takes everything which does not positively interfere with her favourite indulgence. '"Ah, little she'll reck if ye let her sleep on," ought,' says he, 'to be her motto, being applicable to her in the most trying crises of life, even that of the house burning about her ears.'

He contrasts his life, which is a moderately active one, with hers. 'I went up to my dressing-room, about nine o'clock one evening, to prepare to go to a party, when the sound of heavy breathing from the neighbouring apartment informed me that she had reached the land of forgetfulness. I went out, spent a couple of hours in conversation, had supper, set several new conundrums agoing in life, and made one or two new friends. Then I came home, had my usual rest, rose, and set to work in my business-room, where I drew up an important paper. Still no appearance of the lady. I had breakfast, read the newspaper, and played with the children. One of my new friends called, and made an appointment. Still no appearance of my wife down stairs. At length, about the middle of the day, when I was deep in a new piece of business, she peeped in, with a cold nose and fresh ringlets, to ask a cheque for her house-money--having got down stairs rather more promptly than usual that morning, in order to go out and settle her weekly bills. Thus I had a series of waking transactions last night, another this morning--in fact, _a history_--while she had been lost in the regions of oblivion. My sleep is rounded by hers, like a small circle within a large one.'

Sometimes he speculates on the ultimate reckoning of their respective lives. 'Mine,' says he, 'will have been so thickened up with doings of all kinds, that it will appear long. I shall seem to have lived all my days. I fear it must be different with yours. So much of it having been passed in entire unconsciousness, you will look back from seventy as most people do from five-and-thirty; and when Death presents his dart, you will feel like one that has been defrauded of a most precious privilege. You will go off in a state of impious discontent, as if you had been shockingly ill-used.' Such is one of his sly plans for rousing her to a sense of the impropriety of her ways; but all such quips and cranks are in vain. Only don't absolutely shake her in her bed before her thirteenth hour of rest, and you may _say_ what you please. It cannot be implied that she is hardened, for no such quality is compatible with her character. But she smiles every joke and every advice aside with such an air of impassible benignity, that you see it is of no use to think of reforming her in this grand particular.

One day not long since it rather seemed as if she was going to turn the tables on her worthy spouse. She had a remarkable dream, in which she thought she heard a lady sing a new song. When she awoke, she remembered the two verses she thought she had heard, and they turned out to be perfectly good sense and good metre, and not intolerable as poetry. Now this was what Coleridge calls a psychological curiosity, for the verses had of course been composed by her in her sleep. There was more in the matter still. In her waking-life, she has a remarkably treacherous memory for poetry, being seldom able to repeat a single verse even of Isaac Watts without a mistake. Here, however, she had carried two entire verses safe and sound out of her sleep into her waking existence. It was therefore a double wonder. She has accordingly got up a theory, that her mind is at its best in her sleep, and is judged of at a disadvantage in its daylight moments. In sleep lies her principal life. Waking is an inferior exceptive kind of existence, into which she is dragged by the base exigencies of the world. She ought to be judged of as she is in her dreams. No saying what she goes through then. Perhaps she is the most active woman in the world in that state. Possibly she says and does the most brilliant things, such as nobody else could say or do in any condition. 'You say you cannot test it, for you cannot follow me into my dream-world. Well, but it may be as I say; and till you can prove the reverse, I hold that I am entitled to the presumption which my dream-song establishes in my favour.' It must be admitted there is some force in this reasoning. All that her husband can in the meantime say on the other side, is just this: 'Granted the activity and the brilliancy of your sleep-life, it does wonderfully little for me or our household concerns. Only give us an hour more of your sweet company in the forenoon, and we shall admit you to be in your sleep as stirring and as clever as you choose to call yourself.' This of course he says very safely, for he well knows that no earthly consideration would induce her to abridge her sleep even by that one hour.

At a visit I lately paid to this good couple, I found them debating these points, the gentleman still refusing to give implicit credence to the theory which the lady had started in her own favour. The controversy was conducted with a great deal of good-humour, and I could not refrain from entering into the discussion. I started, however, a new theory, which I thought might please both parties, and in this object I am happy to say I was successful. 'Here,' said I, 'is a wife remarkable for putting as much good-nature into her six or eight hours of day-life as most women put into twice the time. No one can tell what she is in her sleep: perhaps the veriest termagant on earth. Suppose her sleep could be abridged, might not some of this termagantism overflow into and be diffused over her waking existence? I can well imagine this, and you, my friend, reduced to such straits by it that you might wish she would never waken more. Be content, then, and rather put up with the little ills you have than fly to others that you know not of.'

THE NEW CONVICT ESTABLISHMENT IN WESTERN AUSTRALIA.

The subject of convict discipline has for several years past excited the attention both of legislators and philanthropists; but the knowledge of the public concerning its details has hitherto been exceedingly meagre. It is not intended in this article to discuss the abstract question of the policy of transportation to the colonies, or of convict discipline there pursued; but merely to give some account of the system adopted at a new settlement in Australia. We will state at once, that our official authority is a Blue Book--one of those huge volumes printed from time to time, by order of parliament, for the edification--or as some facetious folks say, for the mystification--of M.Ps. Having carefully waded through its voluminous pages, we have jotted down the passages that especially struck us, and propose to present the pith and substance of our labour--for it is nothing less--in a condensed and popular form.

Little more than a couple of years ago, it was resolved by government to establish a convict settlement at Fremantle--a small town, as we learn, of some 5000 inhabitants--in Western Australia. The first ship arrived in Swan River on 1st June 1850, with 75 convicts; and in October following, a second came with 100 more. Soldiers, and proper officers to control and conduct the convicts, were on the spot; and a tolerably suitable prison was forthwith extemporised out of a wool-shed or warehouse. It is this kind of temporary and experimental establishment that forms the subject of the published returns to government, which are dated up to February 1851, and include an exceedingly minute and clearly-stated detail of the operations and plans adopted during the six months ending December 31, 1850. Three hundred more convicts--principally from the Portland prison in England--were expected in February 1851, and a grand permanent prison was to be erected, to contain 500 cells.