Page:Popular Science Monthly Volume 24.djvu/198

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186

THE POPULAR SCIENCE MONTHLY.

Jupiter, and the Sun—representing stages of development separated by vast intervals of time, certain regions north and south of their equators are the scene of violent disturbances in their fluid shells or envelopes. But it will not do to liken these phenomena upon the three different globes too closely to one another, for they unquestionably differ not merely in magnitude but in kind and in mode of operation, and this is specially true as to the earth and the sun. We may speak of a sun-spot as a solar cyclone, but we must not forget that it is very different from our West Indian cyclones or East Indian typhoons. The point is that in each case—that of a solidified globe like the earth, surrounded by a comparatively rare atmosphere; that of a partially cooled globe, like Jupiter, enveloped in a dense atmosphere of great depth; and that of a completely gaseous globe like the sun, possessing a sort of shell of partly condensed gases—certain regions near the equator are those in which the greatest disturbance is visible, and in every case, probably, the force of rotation is a powerful factor in the production of these zones of commotion. This shows a sort of survival of the action of certain causes under changed conditions, as a globe proceeds in the process of cooling and condensation from the condition of a sun to that of an unsolidified planet, and so on to the condition of a crusted or solid earth. So, then, we may with some show of reason suggest that the half-belted appearance of the sun last summer was in a certain sense prophetic of its future condition, and that in time its spot-zones will be succeeded by continuous belts resembling those of Jupiter. But no human eye will ever behold the sun thus robbed of his majesty, with his glorious light extinguished by bands of gloomy vapors; for, long before he could reach such a condition, life would cease in the solar system, from want of his vivifying radiations.

The picture of Jupiter here given possesses some interest in itself, as it is a representation of the planet as it appeared in September, 1879, when the celebrated red spot was a very striking object. The spot is seen at the left hand edge of the disk, just above the great southern belt which is narrowed, or indented, in a very singular way, opposite the spot. The red spot is no longer visible, and as it was, perhaps, the most remarkable marking, except the belts themselves, ever seen upon Jupiter, pictures of it will possess great interest in the future.