THE COMETARY SYSTEM.

New Zealand Colonist and Port Nicholson Advertiser, Volume I, Issue 66, 17 March 1843, Page 4

THE COMETARY SYSTEM.

(Continued.) The properties of the ellipse have, even from a very remote period,* been the subject of careful study among geometers, and their acquaintance with them is so far perfected, thatknowing certain circumstances with regard to any portion of an ellipse, or having certain data (as it is termed) in respect to that portion of an ellipse, they can tell the form and magnitude of the whole of the ellipse. Having %se data of any, the least part, they know certainly what'is the whole of the ellipse of which it forms a part. Now, four observations upon one of the heavenly bodies, describing an ellipse,! are sufficient to give an observer at the earth’s surface, these data. Thus then four observations tell him what is the ellipse, which, if it describe an ellipse, a comet is describing. Now, knowing the form and magnitude of the ellipse, he can further, by another known process of calculation, tell all the circumstances of the comet’s motion in it; and if it really move in an ellipse, he can, therefore, tell beforehand, what place it will occupy in it, after any given time. Suppose him to have done this, and to wait until that time, and again then to observe it. If his observations agree with the prediction, he will know that he was right in supposing the comet to describe an ellipse—and that particular ellipse. Now, observations of this kind have for the last two centuries been made upon all the comets which have appeared, one hun‘dred and thirty in number, and the observations on each have been repeated so as to verify one auoiber in a gieat variety of different ways; and the conclusion from all has been the same; viz., that those portions of their orbits, which , the* comets are describing when within our sio-ht, are ellipses;!; ellipses which have all of them the sun for their focus, or rather, for one of their foci—and that the other focus is infinitely far off, beyond the limits of the orbit of the "most distant of the planets. Moreover, that all these ellipses are of the kind which we have described as of great eccentricity , or deviating preatly from circles. Now r , similar observations applied to the planets of our system, show them "also to describe ellipses, having, too, the sun in one of the foci of each ellipse ; hut these ellipses are of exceedingly small eccentricities, or they approximate very nearly to circles. But the elliptic orbit of a comet may lie in an infinite variety of positions in respect to the sun, and yet in all these have its focus m the sun' The length of the ellipse may lie one wav or another, to the right or the left of a line drawn, for instance, from the sun to a particular star, or at any angular distance from that line, or having its plane inclined, at one angle or another, to the plane of the orbit which our earth describes round the sun ; and all these things we are required to know, before we can fix what is the precise path in space along which the comet goes. They are called the elements of its orbit. And on the other hand, knowing these, we do know precisely the curved line which through the years, per-

haps centuries, of each of its revolution, the comet is describing through the fields of space. Nay more, we can tell precisely what part of that path it is at any given time describing; the inward eye remains, as it were, fixed upon it. lono- after it is beyond the reach of the most powerful telescopes. We can tell when it will slowly reach its greatest distance from the sun, or its aphelion, as it is called. Somewhere, perhaps, double or treble the distance of Uranus from us ; and we can tell precisely when it will go through its perihelion, or that extremity of its orbit in which it is nearest to the sun and to us. Now these other elements of a comet’s orbit may all he determined from the same four observations which, ascertained its form and its magnitude. These things have been calculated in respect to one hundred and thirty-three comets, which have appeared at different periods of the two last centuries, and of one hundred and thirty of these, no two are found to describe the same orbit, no two of them are, then, different returns of the same comet. But if two comets, appearing at different periods, had, on examination, been found to be describing, one of them at one period, the same path in space which the other did at the other period; if, moreover, the actual motion of the first comet, known from a previous knowledge of its orbit, ought to bring it precisely to that point of its orbit, where the second comet was, at the time or near about the time when it was seen there, then we should have known that the two comets were, in fact, one and the same comet. Now, although out of one hundred and thirty, no two have thus been found to be the same;

yet-'in the whole nuhiber, one hundred and thirty-three observed, there were three, the identity of which with three others was established. Of these, one is the comet of 1835, or 1759, called Halley’s comet, because he first established its identity with the comet of 1682, 1607, and 1531 ; another is the comet called, for a similar reason, the comet of Encke, and the third is the comet of Biela; the first has a period of about seventy-six years, the second of three years and three-tenths, and the third of seven years and three quarters. Thus, then, we know that there are at least one hundred and thirty different comets revolving continually about the sun, that number of different comets having been seen during the last two hundred years. None of these, except three, have as yet had time to return to us; these three have returned severally at their appointed periods. How many other comets there may he, or what is the whole number of bodies which compose the cometary, as distinguished from the planetary, system of our sun, we know not. Comets have been observed by astronomers only during the two last centuries; one hundred and thirty different ones have during that time been seen, and more are continually discovered, as instruments are perfected and observations multiplied.* Nevertheless, hundreds may, during this period, have escaped observation. Because of their distance, the faintness of their light, or because we eannot observe the heavens in the day, they traverse them so rapidly, that long before the period of the year when that portion of the sky in which they move becomes visible, they are gone.! The comet of Biela could only be found by Sir John Herschel, “ with a reflecting telescope of twenty feet in length, an instrument of enormous power in the collection of light.” What shall we say then of the number and variety of the cometary bodies, which might have been discovered during the two next centuries ? It is quite within the bounds of possibility, that the number of the different comets, revolving continually round the sun, may amount to thousands. Those which are known to us have their orbits lying in every conceivable position in space, subject all, however, to the condition, that one of their foci is occupied by the sun; they have their planes inclined to one another, and to the plane of the earth’s orbit, at every possible angle up to ninety degrees, and the lengths of their orbits are directed towards any and every point in space ; moreover, and this is a singular fact, they have the directions of their motion some oneway, and some another. Moreover, by reason of the elongated forms of their orbits, and their various directions in space, these orbits are made continually to cross one another, and the orbits of the planets, and comets are thus frequently brought into such positions, in respect to the planets, that the attraction of these greatly interfere with, and controls, the attraction of the sun upon them. Now, in all these points of view, the cometary is distinguished from the planetary system of the universe. The orbits of the planets are all of exceedingly small eccentricity; they differ little in form from one another, and none of them much from circles. Their planes are none of them inclined much to one another, or to the plane of the earth’s orbit.} Their orbits never intersect one another, and their distances are such, that the attraction of the rest upon any one must always be greatly less than the attraction of the sun upon it; moreover, all of them describe their orbits the same way, or in the same direction, towards east. These differences between the system of the planets and the system of the comets, are not without a reason ; they involve another and infinitely important distinction between the two systems. The system of planets is stable, the svstem of comets is unstable. ‘ These are terms which must be explained. All the bodies of our system (and from recent observation, it appears of every other), attract one another, each planet is attracted by every other planet, as well as by the sun, and in reality moves more or less in consequence of, and in obedience to, each such attraction, deflecting more or less, continually, from the path which it would otherwise describe, according to the greater or less proximity of the disturbing body. And the aggregate result of these disturbing motions is, an orbit whose general character is that of an ellipse, but which is not in reality an ellipse; an orbit, which moreover, is continually changing, no two successive orbits of a planet round the sun being exactly the same. This continual alteration in the paths of the planets through space, might go on with more or less rapidity, and it might be such, as in its nature, would go on infinitely, so that we might be assured, that our system should never again be what it now is. Nay, a "State of things may be imagined, such as would produce a continual change of this kind, leading necessarily

and- ultimately to its entire destruction. Now we are assured by the most certain reasoning, that the state of things which actually exists, is other than this —that it is a state of things which renders it impossible that the forms of the planetary orbits should continue to change for ever; that, on the contrary, the existing state of things renders it absolutely necessary, that {if nothing else interfere) eventually, after perhaps millions of years, each planet shall again be describing the very same path that it is now describing, and the whole order of planetary disturbances return from period to period, by almost imperceptible degrees, and in an eternal cycle. This condition of the system, is that which is meant by its stability, as the opposite condition is implied by instability. (To be continued.)

Emigration. —England is not decripit, but England is in trying circumstances, and it behoves every one of her children now to render their best services to the State. Distress of the most aggravated character is now existing amongst us in the height of summer, which we have ever been accustomed to regard as the poor man’s harvest, whatever might be his vocation. Go, however, where we will at present, we see no one blithe, but the thoughtless and the worthless ; and, though not of moody pen, we can look forward with little hope to the coming winter. We must not, however, be out of heart —condemn the present ministry, or condemn the last. The fear of both has been that, by adopting emigration as a Government measure, they would ' exhaust the national coffer. Infatuation! We tell Sir Robert Peel that, without emigration, he, with all his ability, will not only exhaust the national coffer, but the parochial coffers also. Here we are at this moment —let the truth he heard —with one man in every eight a pauper, receiving relief by the compulsion of law from his fellow parishioners, who, by the Queen’s letter, are becoming paupers themselves. If something be not very quickly done, almost before winter, we dread the consequence. Sir Robert Peel could not do better than bring in a bill as short as that for the protection of the Queen’s person, for the protection of the people. Let him authorize every parish to anticipate one rate: that is, at once collect two instead of one throughout the country, that one to be appropriated to emigration only. The country is not in a condition to be benevolent, and the rich are hoarding for their evil day. The Queen’s letter for the poor, though benevolently designed, has accomplished nothing; it has not procured sufficient to relieve the town of Paisley through the winter, nay, nor through the summer. It must, therefore, be either a compulsory parochial rate, or a parliamentary vote must be come to, adequate to the occasion. We express no extravagant opinion respecting what only will be a sensible relief from the present pressure of the poor upon the rich and middle classes. It should enable 400,000 people to leave the metropolitan county, England, for the distant colonial counties—Canada, the Cape of Good Hope, &c. What would be the effect of this measure ? That number now costs the different unions, on the average, 71. each per annum. That,therefore, amounts to 2,500,000 Z., which it has cost the parishes to support that number of paupers : in those parishes, also, sustaining a high price of provisions; and, on the other hand, by the competition of parish paupers, debasing the value and the character of the industrious, hard-working, self-sustaining, honest labourer, who, with the inclination to emigrate, has not the means to do so. And, looking on the other side of the question, the carrying of this number to Canada and the Cape of Good Hope might have been accomplished for the very same money. Let the Premier and every other sensible man contemplate the different condition of the pauper had this been done six months ago, of the parishes also, and of the country. The pauper would be a free labourer, at from 4s. to 7s. a day. By this operation the parishes would, by the prompt outlay, have completely relieved themselves from an equal annual charge ; the country would have relieved herself of hungry, and consequently discontented, subjects; shipping would have been called for, the manufacturer would have had orders to supply apparel, hardware, &c.; the colonies would have rejoiced, and the empire would have been strengthened. —Emigration Gazette.

The Printing Press in South Africa. —This was a new era in the mission, and the press was soon called into operation; when lessons, spelling-books, and catechisms were prepared for the schools. Although many of the natives had been informed how hooks were printed, nothing could exceed their surprise when they saw a white.sheet, after disappearing for a 'moment, emerge spangled with letters. After a few noisy exclamations, one obtained a sheet * with which he bounded into the village, showings it. to every one he met, and asserting that, Mr. Edwards and I had made it in a moment, with a round black hammer (a. printer’s ball) and a shake of the arm. The description of such a juggling process soon brought a crowd to see the segatisho (press), which has since proved an auxiliary of vast importance to our cause.— Moffatt's Missionary Scenes.

* Apollonius Pergseus, the author of a most learned treatise on the curves, called Conic Sections, of which number is the ellipse, flourished in the second century, before Christ. f A comet can only be seen by us when it is describing that portion of its elongated orbit which is nearest the sun ; now this portion of its orbit coincides very nearly with the corresponding portion of a certain other curve, called a parabola, and three observations are sufficient, on the supposition that it is a parabola. + This observation will, in the course of this article, be qualified.

* Scarcely a year passes in which one or more new comets are not discovered. t It is related by Seneca, that during a great solar eclipse, sixty years before Christ, a large comet was seen near the sun. . + The inclination of the orbit of Mercury to that of the Earth, is greater than that of any other of the seven greater planets, and it does not much exceed seven degrees.