Page:Popular Science Monthly Volume 30.djvu/39

Rh This theory falls in well with the facts established by Spoerer respecting the motion of the sun-spot zones, and the general, though slow, poleward movement of sun-spots.

Per contra, we have to note that Mr.Lockyer, in his recent lectures on solar physics, reported in "Nature," appears to be ready to accept the old theory that the spots, and their accompanying rings of prominences, are "splashes," due to the fall of meteoric matter upon the sun. He maintains that the spots appear first, and after them the faculæ and prominences; unless the writer is much mistaken, however, the reverse occurs sometimes, and even frequently—first faculæ and then spots among the faculæ.

The question of sun-spots and the weather is still debated with about the same vigor as ever; but, on the whole, there seems to be no reason to modify the opinions expressed in the text. While it is not at all unlikely that careful and continued investigation will result in establishing some real influence of sun-spots upon terrestrial meteorology, it is now also practically certain that this influence, if it exists at all, is extremely insignificant, and so masked and veiled as to be very difficult to determine. There is no ground or reason for the current speculations of certain newspaper writers who ascribe almost every great storm in the eastern part of the United States to some sun-spot or other.

The strange connection between solar disturbances and magnetic disturbances on the earth has, however, become more certain, if possible, than ever before, and is no longer anywhere disputed. In November, 1882, there was a very remarkable instance of an intense magnetic storm and polar aurora, simultaneous over all the earth, and coincident with the sudden outbreak of an enormous group of sunspots.

Mr.Lockyer announces, as the result of a long series of observations upon sun-spot spectra, that there is a striking difference between the spot-spectra at the time of maximum and minimum sun-spot frequency; the lines that are most conspicuous by widening and darkening are by no means the same in the two cases. The most remarkable change is in the lines of iron, which are usually conspicuous, but almost vanish from the spot-spectrum at the sun-spot maximum.

The writer also has ascertained a curious and probably an important fact with reference to the structure of the spot-spectrum. Under extremely high dispersion it is found that the spectrum of the nucleus of a spot is not continuous, but is made up of countless fine, dark lines, for the most part touching or slightly overlapping, but leaving here and there unoccupied intervals which look like (and may be) bright lines. Each dark line is spindle-shaped—i.e., thicker in the middle where the spectrum is darkest and tapers to a fine, faint, hairlike mark at each end; most of them can be traced across the penumbra-spectrum, and even out upon the general surface of the sun. The