CHAPTER IV.

THE STARS-CONTINUED.

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UT what of the actual physical condition of the stars

and suns? Of this but little is known for certain.

The spectroscope, it is true, assures us of the identity of the materials that compose our own sun and its companion stars; and the wonderful conclusion which that instrument reveals to us is the high probability, amounting to all but certainty, that our own sun is an incandescent mass of metal, either partially solid, or in a molten or fluid state, surrounded by an atmosphere of fiery vapour, the chief element of which is hydrogen gas, as shown in the analysis of what are called the red or rose-coloured prominences,* which have been the subject of so much contention, and recent examination at solar eclipses. The fumes of many other metals and gases, however, are likewise to be found, and are distributed in different quantities and proportions to the different stars; and to this is probably owing the difference of colour so perceptible," one star differing from another" in the glory of its colour as much as the glory of its brightness. But in general the same compounds are found to

*These remarkable objects were formerly seen at solar eclipses only; but can now, by an ingeniously constructed telescope, be seen at any time.

exist, in every star that has yet been analyzed by the spectroscope, as are found in our own sun. The metallic substances are chiefly calcium, sodium, magnesia, iron, nickel, copper, zinc, barium, and sometimes cobalt; while hydrogen is generally found in the largest proportions in the huge rose-coloured flames, which we see leaping forth from the body of our sun to the height of from 30,000 to 350,000 miles.

There are, it is true, some who, with Sir W. Herschel, still affirm that these vapours composing the photosphere are merely gaseous; and that the body of the sun, or nucleus, may be cool below. It would not indeed be easy to determine such a question positively; but so far as the evidence of the spectroscope is to be depended upon, the probabilities are strongly against such a supposition. One thing however can be affirmed for certain, -that in every star to which that wonderful instrument has been applied as yet, are found evidence of the existence of the very same metals and gases that are to be found in our own luminary: nay, more, that the very same substances are found deep in the bosom of our own mother earth, and form not only the staple commodity of our planet, but of every star in the sky, and every other planet in our system, from the little aerolite, not bigger than a pistol ball, to the giants of our system that roll above us with their own attendant satellites. The sun therefore may be fairly considered the type of every other star in the heavens, as to the materials of which he is composed as well as his other conditions.

Now what are we to gather from this respecting the nature of those bodies that thus constitute the great element of the second heavens? or what proof have we

of this great fact? What positive evidence can be adduced to prove that the mere brilliant points of light with which the heavens are studded, and which the most powerful telescope cannot magnify or reduce to a disc to the human eye, are surely gigantic suns, the centres of other systems like our sun,-in all respects, except those of relative magnitude, the same. To an ignorant mind, the fact that each one of those twinkling lights is a globe of fire, or flaming metal, not less than a million of miles in diameter, appears so preposterous and absurd, that no reasoning is sufficient to convince an uneducated person; and the statements of astronomers are looked upon by many with a kind of halffaith, half-scepticism, that betrays itself in a lurking smile of incredulity while listening to their wonderful accounts of distance and magnitude. A very little reflection, however, and a slight amount of attention to the subject, or personal observation, will convince the most ignorant or unbelieving of the truth of the great and astounding facts revealed in the heavens on this subject. There are two matters in particular, relating to the stars, which every one should be enabled to understand, and as far as possible realize: viz., the vast size and distance of these bodies. Each of these quantities (if one be proved) would serve to prove the other. Given the magnitude, the distance would be concluded; or given the distance, and the magnitude would be apparent.

Now the actual and precise magnitude of a star could never be ascertained by mere observation of its appearance to the naked eye or in the telescope, from the circumstance that the most powerful telescope makes

no difference in the size of any fixed star which gives no real diameter, that which it seems to give being an optical illusion, which can be demonstrated; but as observations of a planet with a telescope we know perceptibly increases its magnitude, notwithstanding the vast distance of most of them, the inference of infinitely greater distance and consequent magnitude in the case of the fixed stars may fairly be assumed. Even by mere telescopic observation, that which undergoes no change of size, but defies it, under any telescopic power, must plainly be beyond the reach of ocular or optical power; and, whatever they are, must be classed as objects of inconceivable remoteness, and consequent magnitude. But though no real disc of any star has ever been seen, modern science has achieved the grand result without seeing it; and the probable diameter, and magnitude, and even weight of distant stars, can now be all but demonstrated,-not to speak of their actual constitution, or materials of which they are composed, as revealed by the greater wonder of the spectroscope.

The first link in the chain of discovery respecting the stars was the aspect of their enormous distance, from whence their magnitude was thus inferred. And how was this distance ascertained, and what is the conclusion as to their magnitude? Their distance was revealed by what is called their parallax,-by which is meant their apparent change of place relatively to each other, caused by the motion of the earth in space in its annual orbit. The earth in its orbit (as is well known) changes its place from one point to another by a distance varying up to 180 millions of miles. Such a journey, it was calculated, should make a corresponding change in

the apparent distances of the stars from one another, were they within any reasonable distance, as is the case upon the earth. Such changes of place (as is known here upon the earth) are great and rapid and perceptible in proportion to our distance from terrestrial objects, such as rows of trees or masts of ships or chimneys of houses, which seem to change their places, and close up or open out as we move on, if they are ranged on either side of us, those objects that are in front only not seeming to move or change, but remaining stationary.

Again: according as we are near or far from such objects will the apparent change be greater or less, quicker or slower; just as two trees on a distant hill-side will seem to change their position as we move on, more slowly than those two in the neighbouring field; or a steamer on the distant horizon will appear to move more slowly than when leaving the harbour. This apparent change of place and actual motion (caused either by the moving objects we look at when stationary ourselves, or by our own motion in reference to them when they are stationary) are magnified by proximity, and lessened or diminished by distance, until, in a terrestrial landscape, an object in the distance, though really moving swiftly, seems scarcely to move at all; while objects at hand appear to move rapidly, even when they are themselves motionless.

Now to transfer this to the celestial landscape where stars only are the objects. All alike were for a length of time perfectly insensible to either of these tests. Up to the last thirty years, everything relating to the stars remained apparently fixed (without change or motion.) The great distance traversed by the earth, in reference to those at either side of her, produced no

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