THE PLANETS, AS VIEWED FROM THE CENTRE OF THE

V If you were placed, head northward, at the centre of the sun's mass, with its body and luminous atmosphere revolving about you whilst thus yourself without motion,† it is evident that the wondrous phenomena just described (p. 240) would continually be moving from your righthand towards your left; and if, when so situated, your vision were telescopic, and your capability of observation such as to correspond with circumstances so extraordinary, you would see our little globe and its fellow planets, together with their satellites, all holding their courses around you in the same direction as those spots, and over lines of fixed stars which might direct you in mapping down their several orbits for us; because the stars, as seen by you, would differ in no perceptible degree from their present relative positions and magnitudes on our celestial sphere: the line of your distance from us, of 95 millions of miles, being utterly insignificant when contrasted with theirs, and your wonderful observatory and our own, with respect to them, being thus fairly considered as adjacent.-See Illustration, G, on p. 4.

w From our ever-shifting earth the paths of most of the planets often appear to be in "looped curves," devious and mazy; and a long and laborious consideration of circumstances is requisite to unfold the real simplicity of their arrangements and motions; but from your solar observatory all would be seen in beautiful order and harmony. would naturally be led to refer

We may suppose

that you

* For the convenience of illustration, Ferguson has supposed the sun to be transparent, and an observer to be furnished with the means of existing within it, and even of recording his observations! We must hope to be forgiven even for extending so extravagant an idea as this.

+ The sun's mass is agitated about the common centre of gravity of the sun and planets; hence its centre has some motion, but for the sake of simplicity it is disregarded here.

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the various motions visible from your sun-centre to the circular lines in which the solar spots would be moving around you. Now these move, like the several parts of the surface of the sun, and like the knots in the rope of our young friend skipping, (p. 100,) with velocities varying, not with their distances from you at the centre, for they are all alike distant from you; but varying with their several distances from their centres of motion in the solar axis; hence the course of the swiftest of them would point out to you the Solar Equator; and this, or rather the line of stars seen in the same plane with it, might be taken for your standard circle in the heavens, and to it you might refer the orbitual paths of the planets.

* But probably you might still so feel interested in us as to retain our orbit for your standard, and even continue to reckon from our first point of Aries " for auld lang syne." The crossings of the several planetary tracks through the ecliptic or plane of our orbit, are what we call their "nodes." It is evident that in the case of bodies so near as those of our system, their longitudes as seen by you whilst crossing our plane, differ considerably from those points or longitudes at which we see them to be crossing it. Astromers, however, reckon with you; and the point (marked in degrees and minutes from 1° of Aries) at which you would see a planet crossing our ecliptic to go northward or southward of it, is the "longitude of its ascending or descending node." In the same manner, as your minute observation compared the periodical variations in the apparent size and brilliance of any one of these bodies, you would judge that they occurred as it approached the points of its greatest and least distance from your illuminating station; and you might record the longitudes of these unvarying* points the perihelion and aphelion of the planet's orbit.

The "latitude" also, of these bodies. we refer to our ecliptic plane; and the greatest number of degrees of distance from our plane to which any one of them attained as seen from your observatory, would give you the inclination of its path to our ecliptic.

* i. e. not perceptibly varying in the short period of a human life. (See X, p. 259.)

It is evident that, as their residences so revolved around you, the inhabitants of these several little globes must behold your fixed solar station appearing to move in the same direction in the opposite portions of their several ecliptic circles, and that too with angular motions (p. 100) in those several circles, exactly corresponding with their own.

Not one of these planets and satellites would "wax and wane;" nor would the tail of a comet, even like that of 1680, be visible, although extending over 70° of our heavens; for your dwelling-place being the source of their borrowed light, their whole reflecting faces would of course always be presented to you.

Z You would, we suppose, most naturally measure time by the period of the sun's rotation. By attentive consideration of a whole series of observations during very many of these, and thus comparing the several periods in which these several bodies completed their orbits; and remarking that no one of them moved uniformly, but that, as each of them became periodically brighter its motion was accelerated; and that it was retarded also in the opposite and less splendid portion of its path; you might not only infer that those which completed their orbits in shorter times, moved in more circumscribed paths, and consequently were nearer than those which made the slower circuits; but that their movements, as well as their light, were in some way connected with your solar dwelling-place, and even mysteriously dependent upon it.

Sometimes indeed, an undefined cometary body would approach so near, and so rapidly, as to exhibit a most remarkable contrast in its brilliancy and dimensions; and be the occasion perhaps, even of perturbation to your sunny thoughts; but the apparent path even of this would be circular, whilst its form, so rapidly enlarged, as rapidly died away into invisibility.

B Jupiter's superior distinctness and brilliance, compared even with Mercury's, might at first induce you to think that he was the nearest of all the planets, except perhaps Venus; but a comparison of their periods would correct this idea, whilst it led to the consideration of his great distance and superior dimensions; as you would perceive that whilst Jupiter performed one revolution, Mercury performed fifty,

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Venus twenty, the Earth twelve, and Mars nearly six and a half, revolutions.* Beyond this, however, your ingenuity would fail you for want of data :-your position at the centre of our system is disadvantageous, except for the general survey just described.

If imagination, having placed you in the sun, and having also rendered its opaque body and luminous atmosphere alike subservient to you, can suppose you furnished with some means of communication with an astronomizing inhabitant stationed at its northern pole, we know that, comparing his map of the orbits, (for instance, of Mercury, Venus, and the Earth,) with your own taken from the sun's centre, you would find that observation at his distant station, (440,000 miles from your central one,) had displaced, by depressing their paths in the sky, but each to a different amount; and Venus's depression, so caused, being greater than that of the Earth and less than that of Mercury, you might more certainly infer that Mercury was nearer, and the Earth more distant than Venus, &c.

Such are the faculties with which the great Author of his being has invested man that, even in his far-fallen condition, exercised by the very inconveniences attendant on that condition, he has been enabled, not only to understand much concerning the circumstances connected with the motions, and magnitudes, and distances, of these planetary bodies, but also to calculate and predict them with the greatest precision, for distant periods of time. And a handful of sand from the shore, and a weed from the neighbouring rock, furnish him with materials which he has learned to transmute and to model, so as not only to reveal to his gaze much of "the vast and the minute" of the system to which his own little dwelling-place belongs, but the kindred motions of distant systems of circling though centering suns; and far beyond even them, the light of

* Saturn, on the contrary, during one revolution of Jupiter, would not get through nearly one half of his orbit, and Uranus not one seventh of his.

+ See Parallax.

See Double Stars (Index).

numerous other firmaments,* each of them, in all proba bility, crowded with the witnesses of his Maker's benefi cence and power!

Reasons for supposing that the Planets are inhabited.

1. Their similarity of form to each other and to our world--the globular figure being that which affords more surface than any other figure for the residence of contemplative beings:-And the amount itself of their surfaces, which even if, like that of our own earth, habitable only on one fourth part, would accommodate 400 times as many such individuals.

2. They are opaque and solid bodies :-Opaque, from the manner in which their shadows are cast, and from the manner in which they receive shadows: solid, from the manner in which their motions are performed, and from the several attractions which their masses exert on the sun and on each other.

3. The extent of animal existence as revealed by the microscope :-Organic life being discovered wherever there is a superfluity† for its sustenance, at least on the surface of our globe (see pp. 7 and 8).

4. Their several annual and diurnal revolutions :-One common law regulating their motions in their orbits to produce, in exact times, the interchange of seasons; and the rotation of each about its axis, providing for the alter

* See definitions Nebula and Galaxy (page 54).

It is not correct that "every drop of water teems with life":-no microscope can detect animalcules in fresh spring water. The author has, however, frequently seen, at least many hundreds for a moment "at liberty" in so small a portion of moisture as he has wiped on to a piece of glass from the end of a fine needle, which he had dipped into stagnant water and afterwards shaken to throw away its drop:— the next moment shewing only the confused forms of those animalcules, all crushed by the access of atmospheric pressure, in consequence of their film of element having evaporated and thus left them exposed.