Page:Popular Science Monthly Volume 7.djvu/367

Rh sun-spots. A table drawn up by Mr. Loomis, without suspecting their remarkable coincidence, establishes it beyond a doubt.

Nor is this all. Once started on the road, empiric science follows the clew of its deductions. After the auroræ boreales come the cirri, the mare's-tail clouds, of a peculiar form, which float very high in the atmosphere, entirely formed of extremely minute spicules of ice. These have an intimate connection with auroræ boreales, and seem to be in some sort the atmospheric substratum or stage of all their manifestations. It is now endeavored to ascertain whether there does not also exist some relation between the frequency of those clouds and that of the solar spots. In short, there is now, in meteorology, an emulation of discoveries based on these analogies of periods or on the influence of the solar rotation. And we are bound to call attention to this novel tendency of astronomical research, which Donati, a few days before his death, characterized as the advent of a cosmic meteorology—that is, as already stated, of a meteorology in which account should be taken of the multiple reactions of the stars on each other, without limiting those reactions to the habitual forces of attraction and heat.

To this cosmic meteorology evidently belongs Fourier's notion of a combined action which the universe (leaving the Sun out of the question) exercises upon us by its calorific radiations. If the Sun were to go out, the temperature of the solar system would not sink indefinitely—or rather it would not fall to the absolute zero (273°-273° [sic] Centigrade)—but would stop at a certain point, which Fourier estimated at 62° Centigrade below the freezing-point of water. The importance of this temperature must not be estimated by the abnormal figures which measure it: for it appears to be a condition of our very existence, by imposing a limit to the lowerings of temperature produced by the long nocturnal radiation of polar regions. It must be added that Messers.Messrs. [sic] Huggins and Stone have recently justified this bold conception by measuring the heat radiation of several bright stars which they find superior to that of the Moon herself—who ought, one would at first sight believe, to reflect so fair a share of solar heat.

This, then, is the Sun's work. He controls the compass; he marshals the northern lights; he permits or forbids ice-crystal clouds to hover high in the atmosphere; besides performing other offices which we may not at present even suspect. And thus a deeper study of his nature and action tends to modify notably the face of Science, to enlarge our views, and to demonstrate more clearly by what multitudinous links terrestrial existences are connected with the entire universe.—All the Year Round.