What They are not, and what They are.
These phenomena may not arise from disruptions taking place on the sun's surface, neither from violent agitations near that surface. The essential and intimate character of the so-called sun-spots may be found in the interruptions of continuity in the fluid occupying the solar cone-space. This fluid which we call sunlight intercommunicates between the entire opposing surface of sun and earth, unless interrupted by some temporary cause. Any cause which is capable of producing results of such character and magnitude can only act by more or less completely interrupting the development or transmission of this fluid.
The result of such action would be disclosed to us by a decreased brilliancy in the direction of the sun. The so-called sun-spot would be in character, magnitude, form, and shade proportionate to the extent and character of the disturbing force. The permanence or evanescence of the spot would indicate the sun or earth as being the locality of such derangement. The more permanent form being developed at the sun, and the more ephemeral at the earth.
Any forces in operation at the earth which might interfere with the intercommunication of light, would lessen the brilliancy of the light, at the earth-extremity of the cone-space; and the deficiency thus produced would disclose to an observer at the earth all the appearances of a spot upon the surface of the sun. The so-called spot, thus produced, might therefore not be regarded as a veritable spot upon the sun's disc, but rather as an optical illusion.
They are Caused by Magnetic Perturbations.
What may be the forces in operation on the part of the sun, and earth alike, which may so interfere with the development or transmission of light through the solar cone-space?
The condition of the contents contained within the enclosure of the sun-crust and earth-crust, is presumably one of unrest; its actions varying from repose to the most violent agitation, with a tendency to the cyclonic in its motions. Although the earth-core may not be presumed to be an entire moving mass, yet it is known to be in a measure incandescent, and molten. Magnetic storms occur within our earth-crust which sway the needle without, and almost instantaneously manifest their presence over areas of more than half the globe. The same phenomena are undoubtedly present in increased development at the sun.
We may therefore with reason suppose that perturbations, however produced, occur within those spheres, of such an extent and character as might be a sufficient cause of the interruption of development, or of transmission of that fluid.