Page:Popular Science Monthly Volume 1.djvu/165

Rh —the 'things' on the sun—to be the tops of the currents ascending from the sun's body, what changes of appearance are they likely to undergo in the neighborhood of a cyclone? For some distance round a cyclone there will be a drawing-in of the superficial gases toward the vortex. All the luminous spaces of more transparent clouds, forming the adjacent photosphere, will be changed in shape by these centripetal currents; they will be greatly elongated, and those peculiar aspects which the penumbra presents will so be produced."

Mr. Spencer, however, in his article in the former number of, says that at present none of the interpretations of the solar spots can be regarded as established.

"All this is, no doubt, very curious, but it is very remote and unpractical. What have the solar spots to do with me, or I with the solar spots?" exclaims some impatient reader. But suppose it turns out that the spots on the sun do have a very close connection with earthly affairs—what then? The story of these strange appearances is incomplete till this point also is noticed.

The view which connects the spots with cyclonic action is confirmed by the now demonstrated fact that they are mighty solar agitations, whose influence is felt in distant planets. Schwabe has discovered that the spots, instead of being uniform in number and intensity from year to year, have a periodicity increasing to a maximum, and then declining to a minimum in a course of years. The variations consisted in the number of days in the year in which spots were visible, and in the number of groups observed. The indomitable perseverance of this astronomer is something wonderful. The president of the English Astronomical Society, in awarding him its gold medal, said: "For thirty years, never has the sun exhibited his disk above the horizon of Dessau, without being confronted by Schwabe's imperturbable telescope, and that appears to have happened about 300 days in a year So that, supposing he observed but once a day, he has made 9,000 observations, in the course of which he has discovered 4,700 groups." In these observations, he traced three complete oscillations from maximum frequency, through minimum back to maximum again. The period assigned by Schwabe was about ten years, although Prof. Wolf, of Zurich, has showed that 11.11 years (or the ninth part of a century) is indicated rather than a ten-yearly period.

It has been established that there is a coincidence between this sun-spot period and magnetic disturbances on the earth. In every part of the earth the magnetic needle has at any given time a certain definite position, about which, under normal conditions, it will oscillate during the day. Proctor says: