Sun's Physical Constitution.

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period demanded by some geologists, and the general conclusion arrived at by measurement of the sun's heat is that one hundred millions of years amply suffice for condensation of the nebulous mass into the present form.

A process of condensation has not only taken place in the sun, but in all members of the solar system. There has been advance, if the generally received hypothesis be true, in every one from the gaseous to the liquid, from the liquid to the solid. state, to be followed by extinction of their light. There was a time when the sun did not give light in the manner now given; a time when the earth, even if light were given, could not behold it; a time when all the visible glory was invisible; a time when Nature, as now known, was not; in a Source beyond Nature is Nature's origin to be found. Worlds precede worlds in time, worlds lie beyond worlds in space.

Turn to the account-" God made two great lights; the greater light to rule the day, and the lesser light to rule the night He made the stars also. And God set them in the firmament of the heaven to give light upon the earth." The stars seem mentioned lest they should be accounted uncreated. Sun, moon, stars, are classed according to their apparent magnitude and importance. The word "made" is more formative than the word "create." It is used for

dressing," "arranging," "making ready." The calf was dressed for Abraham's mysterious visitors, and the cakes were made of meal (Gen. xviii. 6, 7). The same Hebrew word, used for "dressing," "making," "crowning," informs us that the sun was dressed, made, crowned ruler, to give light on the earth. By the time earth and water were separated, and dense vaporous clouds rarefied, the earth's mass attained a measure of consolidation, and began to exhibit vital power in lowest forms of vegetable organisms; the sun, clearing the photosphere, sent rays of light and heat through the vast pressure of his own vapours, and became lord of the day.

The Sun's Physical Constitution.

The actual density is about one-fourth that of the earth, or a little greater than the density of water.1 The tremendous

The sun is 1,260,000 times larger than the earth, and 882,000 miles in diameter. More than 1,200,000 earths would be required to form the substance

heat, whatever pressure the gases and vapours are subject to, renders a solid nucleus improbable; and we must regard the sun as, in the main, a gaseous body. Around it is no permanent or solid crust, but an envelope continually pierced by blasts and jets from within. This great mass, swaying our system, is compressed towards the centre, but hardly any definite theories can be adopted concerning any other than its gaseous condition. The attractive and repulsive forces are such, and the elements exist in forms and quantities with which we are so nearly unacquainted, that when one difficulty is removed from our understanding it gives place to another. The sun's envelope cannot, in any ordinary sense, be counted a crust at all; but as the vaporous globe is in the presence of the cold of space, there is necessarily a process on the outer surface corresponding to the formation of clouds in our skies. The vapours composing them are chiefly metallic elements, which condensing may descend in sheets of fire, and form a nearly continuous envelope, through which the central imprisoned gases are erupted with great violence. Mr. Proctor states "The sun is a gigantic bubble whose walls are gradually thickening, and its diameter diminishing, at a rate determined by its loss of heat. It differs, however, from ordinary bubbles in the fact that its skin is continually penetrated by blasts and jets from within." 1

Sir W. Herschel viewed the sun as a solid globe, around which lies an atmosphere of complex nature. He thought that the real body of the sun was neither illuminated nor heated very greatly. "Whatever fanciful poets may say in making the sun the abode of blessed spirits, or angry moralists devise in pointing it out as a fit place for the punishment of of one sun, and the weight or mass is 300,000 times greater than that of the earth. Our sun is not a large star compared with others, for Sirius is equal in bulk to more than 4000 suns. The surface of the sun is about 2,284,000,000,000 square miles, there are 3,097,600 square yards in every square mile, and on every square yard a heat is produced equal to that which would be caused by burning on it six tons of coal an hour. The impact of matter falling into the sun merely from the earth's distance, would give 6000 times the amount of energy which would be produced by mere burning. The sun travels at the rate of 154,185,000 miles the year. His mean distance from the earth is 91,430,000 miles; rotation on the axis occupies about 25.38 days.

"The Sun a Bubble:" R. A. Proctor.

the wicked, it does not appear that they had any other foundations than mere opinion and vain surmise; but now I think myself authorised, upon astronomical principles, to propose the sun as an inhabitable world." Sir John Herschel, the son, took a wholly different view as to the coolness of the sun; and, incredible though it seem, regarded certain bright objects, shaped like willow leaves, lying athwart and across each other, as the immediate sources of the solar light and heat. He says "We cannot refuse to regard them as organisms of some peculiar and amazing kind; and though it may appear too daring to speak of such organisations as partaking of the nature of life, yet we do know that vital action is competent to develop at once heat and life and electricity."

The sun's surface has not only spots which have a central part and a fringe less dark; but also contains certain bright streaks, by some called faculæ, in the neighbourhood. of the spots. "The sun-spots are really hollows or cavities in the solar atmosphere where the temperature of the glowing gases has been reduced." The spots are said to be confined to two definite zones, extending about 35° on each side of the equator : a scene of solar tornadoes of white-hot hydrogen, which blow with such fierceness that, compared with these, our most destructive storms are summer breezes. The spots are certainly depressions of greater or less depth, and the light received from the umbra of a spot shines through absorbing vapours. "A great difficulty lies in the fact that we have no clear evidence to show whether the sun-spots are formed by forces acting from without or from within, . . . whether the seat of that action which leads to the formation of a spot lies below or above the level of the photosphere. . . . As to the prominences, it seems to be demonstrated that some are mere clouds in the upper regions of the solar atmosphere, while others are due to some form of eruption, and only assume the cloud form after the eruption which gave them birth has ceased." There are bridges, arcs, stalks, leaves, and veils of clouds, most intricate in structure. The wildest and most fantastic variations take place, renewals of fresh forces with "Spectrum Analysis," p. 263: Henry E. Roscoe. "The Sun," pp. 438, 439: R. A. Proctor.

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scenes of tremendous tornadoes, swift rushes of glowing vapours and cyclonic motions. The least spot, perceived with the most powerful telescope, has an area of fifty thousand miles; those visible to the unaided eye are enormous. The largest spot recorded had a greater breadth than 143,500 miles. The spots sometimes burst in pieces, like a piece of ice dashed on a frozen pool, and disappear in a moment.

The eruptions, which occur at all times, are vast explosions, seeming to come from some twenty thousand miles below the edge of the sun's disc, and extend many thousands of miles in every direction. There are brilliant, silver, copper, and rubycoloured coruscations. The velocity has been known to exceed two hundred and fifty miles a second. They are of glowing hydrogen, and other vaporous elements, through an atmosphere of hydrogen.

Coloured prominences consist of glowing gas of various tints. and forms-their origin is still a mystery. The sierra, or rugged line of projections, is made up of ranges of red and other coloured flames, now called the chromosphere. The whole disc of the sun is much marked with roughness like an orange, and some of the lower parts of the inequalities are blackish. The faculæ are ridges of elevation above the rough surface, and sometimes, next to a spot, will be a protuberant lump of shining matter.

Many metals exist in the sun, more than thirty have been. found of the fifty-one known on earth. The sun is made chiefly of metals; in our earth metals form the minority.

The surface of the sun is exceedingly complex. Analysis of spots shows three envelopes within the photosphere: the penumbral fringe, the dark umbra, the so-called black nucleus about ten thousand miles below the photosphere. The photosphere is a fourth solar level. The fifth is a shallow atmosphere discovered by Young, extending three or four hundred miles above the photosphere. Sixth, the sierra, about eight or ten thousand miles. Seventh, the prominence region, extending to a height of thirty or forty thousand miles, with occasional extension to more than a hundred thousand miles. Eighth, the inner brighter corona, from two to three hundred thousand miles, expanding in places to four

Counterpart in the Planet Saturn.

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or five hundred thousand miles. Ninth, the outer radiated corona, jagged in outline and extending fully a million of miles from the visible glowing surface of the sun. All these envelopes are themselves multiple; and the outer corona is but the inner part of a solar envelope, or appendage, with outermost limits lying altogether out of ken. What a complex subject of research lies before our astronomers!

The sun has almost a counterpart in the planet Saturn, whose splendid architecture displays the fashioning power of the great laws of the universe. The beauty of the system, the marvellous gigantic rings, the delicate varieties of colours in the rings and in the planet, the singular problems suggested by their magnificent size, fascinate the observer. If the vast belts are not cloud-masses formed by the sun, their real origin must be in some action of the planet's own mass. The heat of his surface may cause currents of vapour to rise continually; on attaining the upper regions of his atmosphere, they are condensed in the form of a cloud. "A similar peculiarity exists in the case of the sun. Indeed, a somewhat surprising resemblance exists between Saturn and the sun, as regards many important characteristics. The planet, like the sun, is of low specific gravity-very far lower than the earth's; as the sun has eight primary attendants, so Saturn has eight satellites; and as the sun has his attendant disc of minute bodies (seen in the Zodiacal light), so Saturn has his ring system, in all probability, of multitudes of minute satellites travelling in independent orbits around him. Is it not possible that the relation necessary to make the analogy complete may be actually fulfilled, and that Saturn is a source whence heat is supplied to the orbs which circle around him?"1

The analogy may be added to by a further fact-Jupiter, with his dark bands, seems now to be in the same state as was our earth. His cloudy shifting streaks; and the appearance, at times, as of mountains or openings; may be inaugurating new days and nights in that far-off mighty planet.

It is not necessary, for those who believe that all things are of God, to adopt any scientific theory as final. Mayer and Thomson maintained that the sun's heat, compared with 'Essays on Astronomy," p. 93: R. A. Proctor.