| Mercury | 36,700,000 | |
| Venus | 68,770,000 | |
| The Earth | 95,000,000 | |
| Mars | 144,780,000 | |
| Jupiter | 494,000,000 | |
| Saturn | 906,000,000 | |
| Uranus | 1822,000,000 | |
| Neptune | 2850,000,000 |
It will be seen, however, that in this table of distances there is one great exception to the rule, namely the distance between Mars and Jupiter, which is nearly double what it should be according to this rule, giving rise to the idea that a planet ought to be placed between them. Professor Bode was so convinced that something of the kind was necessary to complete the harmony of the series, that he caused to be instituted a search for the supposed planet, and according to his conjecture one was discovered as nearly as possible in the situation indicated, but upon more accurate information being obtained, this planet was found to be so small (scarcely 150 miles diameter) that it could hardly be considered as a planet ranging with the others, and having so large a space of the heavens to itself; shortly afterwards another small planet was discovered, having nearly the same orbit. From time to time others have been discovered, to the number of forty-two, up to the present date. Dr. Olbers upon discovering the second of these small bodies, where one great one was anticipated, put forth the curious hypothesis, that one large planet had really existed there at some former time, that it had been shattered into pieces by some accident, such as an internal explosion, and that more of these pieces would be found; it is curious how accurately this prediction has been verified.
If we suppose the original planet to have been liquid when shattered to pieces, it would fully account for the fragments being spherical, just as globules of mercury assume this form from their own attraction of gravitation, and that the planets, our own earth amongst them, are liquid, is very nearly proved by their forms, which are exactly such as fluid masses rotating on an axis would assume, moreover the specific gravity of some of the planets is but little more than that of water, and with respect to our earth, the evidence of internal heat, increasing as we descend below the surface, &c., show almost beyond doubt that at the present time it is in a liquid state (molten) covered over by a few miles' thickness of hardened crust, which bears such a small proportion to the bulk of the globe, that the whole may be considered as liquid.
THE STELLAR SYSTEM.
The thousands of stars which spangle the heavens are all part of one "system;" but it has been found by the aid of the telescope that this system is but one out of many. Our system of stars occupies a space somewhat in the form of a thick lens or much-flattened sphere, but others are of very different forms, and some have but little regularity of form at all; our sun is one of the stars of this system. It is not known whether there are planets revolving round the other stars, the distance being far too great for any telescope to render them visible. Our sun occupies a somewhat central position in the system. The stars are classed into sizes, as first magnitude, second magnitude, &c., on to the thirteenth or fourteenth magnitude, but all beyond the fifth magnitude (by far the greater number) are only visible by the aid of the telescope. There are about 5000 stars visible to the naked eye. But fourteen stars of the first magnitude are in our hemisphere of the heavens, and about fifty of the second, but the number of stars of each magnitude increases prodigiously in the higher numbers, so that those stars capable only of being seen by the aid of powerful telescopes, amount to many millions; these are chiefly situated in a great belt which encircles the heavens, called the "Milky Way," which is caused by the line of vision passing through the breadth of our starry system, and consequently meeting with a greater number of stars than in other directions, where it only crosses its thickness.
The other systems of stars, called "nebulæ," from their resemblance to little clouds, were supposed to consist of luminous matter of but little density, and which might at some future period be condensed into stars; but the improved power and construction of telescopes have enabled astronomers to resolve many of these nebulæ into clusters of stars, and there is but little doubt that all could be thus resolved, were the telescope of sufficient power; and thus it appears that in the infinity of space collections of systems are placed, each one too distant from the others to be calculated or written in numbers, but each consisting of thousands of suns many hundred times greater than this earth, and many millions of miles from each other. What an idea of space does this afford, and how soon do all our narrow notions of possibility and impossibility vanish before such facts accomplished by the hands of God!
FIG. 24.