Page:Popular Science Monthly Volume 11.djvu/368

354 therefore "the supposition of the existence of this light in the plane of the sun's equator does not satisfy the observations made." The closing sentence of his very interesting article gives the first intimation that the zodiacal light has a near connection with our globe. Housseau says:

This notice is the only one, of any importance whatever, that was taken of the zodiacal light for many years, with the exception of some experiments made to ascertain whether there is any heat connected with it—experiments which we think resulted in establishing the fact that it is near enough to emit heat sufficient to affect a thermo-electric pile of twenty-five pairs, causing the needle of the galvanometer to indicate 12° when the pile was directed toward the base of the zodiacal light.

We come now to a consideration of the observations taken during the cruise of the Japan Expedition, and we hope our readers are not weary of the subject; for, if it can be demonstrated that we have a ring of nebulous matter around our globe at a distance of 150,000 to 200,000 miles, there are many inquiries growing out of that fact full of interest, and yet to be answered by experiment and induction. It will be a matter, then, to be considered whether it is self-luminous—that is, of the nature of the sun's photosphere—or whether it shines only by reflected light, like the rings of Saturn; whether it is increasing or diminishing in magnitude and extent. If it is shown to be self-luminous, we will then wish to know whether it may not be widening and extending itself, at the same time increasing in its capacity to emit both light and heat, until it envelops the entire globe, modifies climate, melts the icebergs and snows of northern latitudes, and dispels darkness from our globe. We may inquire, too, whether it may not be used as a grand instrument in the hands of the Creator for the future development of his purposes in regard to our globe. It may also be an inquiry whether it does not already influence the magnetic state of the earth, and play an important part in the causes producing the aurora borealis. These and many more similar questions will arise from the establishment of the fact that the zodiacal light emanates from a ring of nebulous matter so near our earth. Let us, then, give our author a close examination and a patient hearing, that we may be enabled to form a correct judgment as to the truth of his deductions.

We have not space to present all the reasoning by which our author shows that the zodiacal light cannot be produced by a ring of