Page:Popular Science Monthly Volume 24.djvu/195

Rh spectrum. In a communication to the French Academy of Sciences, M. Thollon says that an hour before his observation on the C-line he had observed in the same region a slighter displacement not only of the lines of hydrogen and of the b-group but also of the coronal line 1,474. He observed on several days other remarkable spectroscopic phenomena, and noticed that nearly the whole southern half of the sun's disk gave manifest signs of violent agitation. In view of these facts, it seems surprising that little apparent effect was produced upon the earth by these solar outbursts. Two or three times in 1882 the earth responded instantly with magnetic storms and brilliant auroral displays to the solar activity, but this year the great sun-spots and their accompanying phenomena have shown comparatively little power to affect terrestrial magnetism.

Fig. 1 shows the sun as it appeared on the 16th of July, when the advancing procession of spots had reached two thirds of the way across the disk.

Fig. 2 represents the sun on the 20th of July, when the spot belt extended completely across the disk.



Fig. 3 shows the appearance of the sun on the 25th of July, when more than half of the procession had disappeared around the western edge, and the great group bringing up the rear was near the meridian.

In the latter part of August and early in September a row of spots, principally in the southern hemisphere, was again seen upon the sun, but it was shorter, more crooked, and composed of fewer spots and groups, than the great belt of July.

There is one point of view from which the sun-spot belt just