Page:Popular Science Monthly Volume 13.djvu/359

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ON THE FORMATION OF NEBULÆ.

This is the general rule for the formation of secondary bodies in all systems. In our system there seems to have been one exception to this general rule, viz., the asteroids. From some cause—most probably from external disturbance—this ring did not collect into a single mass, or, if so, was dashed into many fragments afterward by some meteoric or cometary body which, thrown out from some previously-formed nebula, had been wandering through space till it reached our system.

There are indications in other parts of the system of such external disturbances, notably in the satellitious system of Uranus.

From the manner in which the solar system has been formed, it seems most probable that all the bodies in it should both revolve and rotate in the same plane and direction that the sun does, had there been no external disturbance to prevent it.

Having examined the mode in which a planet is formed, and thus learned how a solar system may be formed out of nebulous matter, and having discovered that the system must be contracting into smaller dimensions from some sufficient cause, let us next inquire what consequences are most likely to follow the operation of such cause.

Consequences of Contraction.—It has been shown, by the foregoing investigation, that our system is expending its life-giving energy on some resisting medium which causes this contraction.

This, at first sight, seems saddening to contemplate; but there may be another point from which to view it. For, while it is seemingly wasting its life-giving power in this struggle with resistance, it may, in reality, be storing up a new supply of potential energy, by which a future activity may be insured. Or, in other words, it may be forming a new bud, which, when properly vivified by another one, may blossom forth with the most brilliant rainbow hues, and finally ripen into planetary fruit which shall become the happy home of future intelligent races.

Modus Operandi of Conservation.—It is well known that the stars are not fixed, but that they are moving in various directions with various velocities, relatively to our galaxy, at least.

Now, if the stars be moving, it is very probable that some of them are moving in such directions that they will finally meet, either in pairs or otherwise.

Let us direct our attention to two of them which are very like our star in mass and attendants, or we may suppose our sun to be one of them, and that they are so moving as to approach each other at the very slow rate of one mile a week; and let us further suppose that, before meeting, each will have arrived at that state of quiescence to which all systems are tending.

The object of assuming such slow original motion for the meeting bodies is to make a test case, as it were, in order to show clearly that the gravitative force of two such large bodies is sufficient to convert them both into a nebulous mass, besides throwing large portions of