and that what wesee is the dazzling surface of this fiery ocean. But the telescope reveals spots darker than the surround

ing spaces, and sometimes many thousand miles in diameter. Figure 67 shows how a spot may be traced from day to day, as it traverses the disk of the Sun from east to west, its changes revealing the fact that it is a real depression in the luminous surface. These spots were at first conjectured to be scoria, masses of dross, floating on the burning sea. But closer observation showed that they have a dark center, and lighter borders, and as the Sun revolves assume the different aspects of vast excavations.

To explain these facts the theory was adopted by Herschel and others, that the body of the Sun is invisible, and that the light and heat come from a luminous atmosphere, the spots being temporary openings in this atmosphere, disclosing the darker surface of the Sun itself. And astronomers that were devout as well as scientific have fancied that under this glow

ing canopy of flame, and defended from its fervors by intervening spaces filled with some ethereal fluid that does not permit the intense heat to pass downward, is the home of the redeemed, the city that hath foundations.

Another advance was made, and this dream faded into thin air. It became an axiom in science that no force operates unspent. The Sun evolves every moment enormous amounts of light and heat, which, on all the principles that science teaches, no mere stratum of fiery clouds could send forth from age to age without diminution. Meanwhile instruments and methods continued to improve; the spectroscope began to reveal its wonders, errors were detected, and new phenomena discovered, until, at the present hour, we are justified in saying, in paradoxical language, that we know more about the Sun and know less about it than ever before.

Modern methods treat of the Sun under three heads: the photosphere, the chromosphere, and the corona. The photosphere is the disk of the Sun, visible with or without the telescope. To the unaided eye it seems a round, smooth, shining mass. Seen through one of the larger telescopes the surface presents a mottled aspect, which has been compared to the appearance of rice grains floating in water, or leaves of the willow-tree, interlacing each other in all directions. Traversing this surface, as the Sun revolves, are the spots already described, often enlarging, or diminishing, or even disappearing as they go. What causes them we know not; science may safely multiply conjectures, because proof and disproof are alike hard to discover.

A few years ago the spots were regarded as furnishing the means of ascertaining the time of the Sun's rotation on its axis; but later observations have demonstrated the surprising fact that the regions nearer the poles revolve more rapidly than the equator. Moreover, the equatorial belt does not seem to rotate always in the same period of time, the variation being sometimes twenty-four or even thirty-six hours. For the cause of this there is not even a plausible conjecture. Faye's idea of ascending and descending currents only originates new questions in regard to the nature of the strata, and the cause of the currents. And then there is something in the color of the lighter portion of the spots which is inexplicable. Instead

of a gradual shading off from the surrounding brightness to the dark center, the border is marked with parallel lines, which give it an appearance like that of the lower edge of a thatched roof.

Besides the wonders on the very surface of the Sun, observations made with powerful instruments in the time of total eclipses have discovered new marvels. At the moment of total obscuration the dark disk of the moon is found to be surrounded with a halo of silvery light.

This halo is some

times seen extending on all sides to the apparent distance of

half the diameter of the Sun.

What this corona, as it is called,

is composed of, no one can tell.

It is not an atmosphere in

any degree like that of the Earth. A stratum of any kind of

gas, held in place by gravitation, would maintain a uniform height from the surface; whereas the corona presents a very irregular outline.

There are, also, visible during total eclipses appearances which have received various names, "prominences," "flames,"

"protuberances," etc. These sometimes rise to the enormous height of fifty thousand miles above the surface of the Sun.

When astronomers discovered them, the first thought was that they are clouds of some sort, floating upward from the fiery deep, and reflecting its rosy, light. The spectroscope shows that this is an error, and that these enormous columns, fantastic and variable in their forms, are masses of hydrogen gas, so hot as to shine by their own light. And nearer the body of the Sun, close above the burning surface, there seems to be a stratum of this same gas, intensely heated, from which shoot up, from time to time, these mighty tongues of flame. This is called the chromosphere. The spectroscope reveals another fact. While it shows that hydrogen, iron, and some other substances well known to us, enter into the composition of the Sun, there are many lines in the spectrum which are not recognized as belonging to any element of this earthly creation. What they are none can even conjecture.

In short, the sun is the scientific crux philosophorum. To the unaided eye it seemed calm, silent, powerful, shining upon the worlds in its stillness and strength. Viewed through the lenses of the astronomer, it is an ocean of flame, swept by currents compared with which our Gulf-stream is only a ripple in a summer brook, and tossing perpetually with wilder tempests than earthly oceans feel when wrecked navies strew the shore. From time to time, here and there, from the hot deep there open wide mouths, as of volcanoes, into which a world like this might fall, and from them issue masses of flame that leap upward thousands of miles, and throw their light to the stars. What fuel feeds this fiery furnace; what power within bursts forth in these floods of light and heat; what winds sweep these seas of flame, no mortal can tell. Science can only watch from afar the rush and rage of the storm, and realize the narrow limits of human knowledge.

Is it possible to present in language any adequate idea of the scale on which natural operations are here carried on? If we call the chromosphere an ocean of fire, we must remember that it is an ocean hotter than the fiercest furnace, and as deep as the Atlantic is broad. If we call its movements hurricanes, we must remember that our hurricanes blow only about a hundred miles an hour, while those of the chromosphere blow as far in a single second. They are such hurricanes as, coming down upon us from the

66

north, would, in thirty seconds after they had crossed the St. Lawrence, be in the Gulf of Mexico, carrying with them the whole surface of the continent in a mass, not simply of ruin, but of glowing vapor, in which the vapors arising from the dissolution of the materials composing the cities of Boston, New York, and Chicago, would be mixed in a single, indistinguishable cloud." When we speak of eruptions, we call to mind Vesuvius burying the surrounding cities in lava; but the solar eruptions, thrown fifty thousand miles high, would ingulf the whole earth, and dissolve every organized being on its surface in a moment. When the media

they gave rein to their wildest imagination, without reaching any conception of the magnitude or fierceness of the flames around the sun.-P. 262.

With this eloquent passage from the author we leave the vast problem. What science may hereafter achieve we know not; nor is it safe to say at what point its victories must cease. We can only say that in the present state of science the solar mysteries are not solved. Professor Newcomb gives the views of four distinguished students of the Sun, Rev. Father Secchi, of Rome; M. Faye, of Paris; Professor Young, of Dartmouth College; and Professor Langley, of Allegheny Observatory; to which the still later theory of Dr. Henry Draper, of New York, is appended, stating his discovery of glowing oxygen in the Sun, by means of the spectroscope. These theories differ one from another in some degree, and from some of the views expressed by our author; but these differences only reveal more clearly the magnitude of the difficulty. The spirit of all these able men is well expressed in a single sentence of the closing paragraph of Professor Young's paper: "Such, in brief, are my opinions; but many of them I hold with little confidence and tenacity, and anxiously await more light." This modesty distinguishes the true scientist from the pretender. A quack knows every thing.

THE PLANETS.-As has been already stated, investigation has found an error in the former measurements of the Solar System, and we are compelled to reduce the figures all along the line. These later investigations have detected some other errors, and made important discoveries, and achieved great advances; and yet, as regards the sum of what we think we