FORM, EXTENT, ETC., OF THE ZODIACAL

LIGHT.

earth, seems to be that of a lens; or rather that of a huge wheel, thickest at the center, and thinned down to an edge at the outer extremities. Its being seen edgewise, and only one-half at a time, gives it the appearance of two pyramids with their bases joined at the sun. It is an interesting fact, stated by Prof. Nichol, that this light or nebulous body lies in the plane of the sun's equator. A line drawn through its transverse diameter, or from one apex of the pyramids to the other, would cross the axis of the sun at right angles. This fact

would seem to indicate a revolution of this curious substance with the sun upon his axis.

Let A. in the above cut, represent the sun, BB his axis; then CC will represent the extent, and DD the thickness of this curious appendage.

325. At the meeting of the American Association for the Advancement of Science, held in Providence, R. I., August 18, 1855. The Rev. George Jones, of the U. S. navy, read an elaborate paper upon the Zodiacal Light, founded upon his own observations during a cruise in the United States' steam frigate Mississippi, from 41° N. lat. to 52° S. lat. From a record of 331 observations, each accompanied by a drawing, showing the exact form and position of the Light among the stars, Mr. Jones was decided in the conviction that the Zodiacal Light is a luminous ring around the earth, like that which surrounds the planet Saturn. Prof. Pierce, of Harvard College, is said to have concurred with him in this opinion.

326. After all the observations that have been made,

325. Mr. Jones' observations? Extent? Where made, and when? Prof. Pierce's reported opinion?

and the theories that have been advanced, it must be admitted that the subject of the zodiacal light is but imper fectly understood. Prof. Olmsted supposes it to be a nebulous body, or a thin vapory mass revolving around the sun; and that the meteoric showers which have occurred for several years in the month of November, may be derived from this body. This is the opinion of Arago, Biot, and others.

The best time for observing the zodiacal light is on clear evenings, in the months of March and April. It may be seen, however, in October, November, and December, before sunrise; and also in the evening sky.

THE SUN'S MOTION IN SPACE.

327. Although, in general terms, we speak of the sun' as the fixed center of the system, it must not be understood that the sun is absolutely without motion. On the contrary, he has a periodical motion, in nearly a circular direction, around the common center of all the planetary bodies; never deviating from his position by more than twice his diameter. From the known laws of gravitation, it is certain that the sun is affected in some measure by the attraction of the planets, especially when many of them are found on the same side of the ecliptic at the same time; but this would by no means account for sɔ great a periodical notion.

328. In addition to the motion above described, the sun is found to be moving, with all his retinue of planets and comets, in a vast orbit, around some distant and hitherto unknown center. This opinion was first ad vanced, we think, by Sir William Herschel; but the honor of actually determining this interesting fact belongs to Struve, who ascertained not only the direction of the sun and solar system, but also their velocity.

326. Is this subject well understood as yet? Prof. Olmsted's theory? When the best time for observing the zodiacal light?

cts?

827. Is the sun really stationary? What motion? How affected by plan828. What other motion? Who first advanced the opinion that he had sich a motion? Who demonstrated it? Toward what point is the sun and

The point of tendency is toward the constellation Her cules, right ascension 259°, declination 35°. The ve locity of the sun in space is estimated at 8 miles per second, or 28,000 miles per hour. Its period is about 18,200,000 years; and the arc of its orbit, over which the sun has traveled since the creation of the world, amounts to only about th part of his orbit, or about 7 minutes-an arc so small, compared with the whole, as to be hardly distinguishable from a straight line.

329. With this wonderful fact in view, we may no longer consider the sun as fixed and stationai y, but rather as a vast and luminous planet, sustaining the same relation to some central orb that the primary planets sustain to him, or that the secondaries sustain to their primaries. Nor is it necessary that the stupendous nechanism of nature should be restricted even to these s.blime proportions. The sun's central body may also have its orbit, and its center of attraction and motion, and so on, till, as Dr. Dick observes, we come to the great center of all -to the THRONE OF GOD!

Professor Madler, of Dorpat, in Russia, has recently announced as a discovery that the star Alcyone, one of the seven stars, is the center around which the sun and sviar system are revolving.

NEBULAR THEORY OF THE ORIGIN OF THE SOLAR SYSTEM.

330. It was the opinion of La Place, a celebrated French astronomer, that the entire matter of the solar system, which is now mostly found in a consolidated

solar system tending? Its velocity? Period of revolution? Amount of its progress since the creation of the world?

329. How, then, should the sun be considered? How extend the analogy: What further recent discovery, and by whom?

880. State the "nebular theory" of the origin of the solar system? Who first started this theory?

ORIGIN OF THE SOLAR SYSTEM- -NEBULAR THEORY. 157

state, in the sun and planets, was once a vast nebula or gaseous vapor, extending beyond the orbits of the most distant planets-that in the process of gradual condensation, by attraction, a rotary motion was eng ndered an imparted to the whole mass-that this motion caused the consolidating matter to assume the form of various concentric rings, like those of Saturn; and, finally, that these rings collapsing, at their respective distances, and still retaining their motion, were gathered up into planets, as they are now found to exist. This opinion is supposed to be favored, not only by the fact of Saturn's revolving rings, but by the existence of the zodiacal light, or a resisting medium about the sun; and also by the character of irresolvable or planetary nebulæ, hereafter to be described.

331. To this theory, however, there are many plau sible, if not insurmountable, objections.

(a.) It seems to be directly at variance with the Mosaic account of the creation of the sun, moon, and stars. The idea that the sun and all the planets were made up, so to speak, out of the same general mass, not only throws the creation of this matter back indefinitely into eternity, but it substitutes the general law of attraction for the more direct agency of the Almighty. The crea tion spoken of in the Bible thus becomes not the origi nating of things that did not previously exist, but the mere organization or arrangement of matter already existing.

(b.) The supposed consolidation of the nebulous mass, in obedience to the general law of attraction, does not of itself account for the rotary motion which is an essential part of the theory. Under the influence of mere attraction, the particles must tend directly toward the center of the mass, and consequently could have no tendency to produce a rotary motion during the process of conden

sation.

(c.) The variation of the planetary orbits from the

881. What said of it? State the first objection named? The second' Third Fourth? Fifth? What remark added by the author?

plane of the sun's equator contradicts the nebular theory. If the several primary planets were successively thrown off from the general mass, of which the sun is a part, they could not have been separated from the parent body till they were near the plane of its equator. Now, as the sun is assumed to be a part of the same mass, revolving still, the theory would require that the portions now separated from him, and called planets, should still revolve in the plane of his equator. But instead of this, it is found that some of them vary from this plane to the amount of nearly 42°.

(d.) This theory assumes not only that the primary planets were thrown off from the parent mass by its rapid revolution, but that the primaries, in turn, threw off their respective satellites. These, then, should all revolve in the plane of the planetary equators respectively, and in the direction in which their primaries revolve. But their orbits not only depart from the plane of the equators of their primaries (Jupiter's satellites excepted), but the moons of Uranus actually have a retrograde or backward revolution.

(e.) If the sun and planets are composed of what was originally the same mass, it will be necessary to show why they differ so materially in their physical natureswhy the sun is self-luminous, and the planets opake.

But we have not room to discuss the subject at length in this treatise. It is but justice, however, to say, that men eminent for learning and piety have advocated the nebular theory, in the belief that it is perfectly consistent with the Mosaic account of creat.on. But the writer is frank to state, that while he acknowledges the force of some of the considerations urged in its support, he has not yet seen reason for adopting this theory of the origin of the solar system. Through faith we understand that the worlds were framed by the word of God [not by the law of gravitation], so that things which are seen were not made of things which do appear [or of pre-existing matter]."-Heb. xi. 3.

66

332. Upon the supposition that the sun and planets were created as they are, by the direct act of God, an