Page:Popular Science Monthly Volume 2.djvu/620

600 (helium) which hitherto has been unknown on the earth. Moreover, also, the inner structure of the sun, the distribution of its incandescent, liquid, and gaseous parts, its luminous and colored envelop, the nature of its spots and protuberances—all this is no longer a play-ground for fantastic imaginings, but the subject of exact research. Since the great eclipse of 1868, Lockyer and Janssen, Zöllner, Huggins, and Father Secchi, have observed, day after day, storms, whirlwinds, flame-sheaves, outbursts of burning hydrogen to the height of 20,000 miles: thus has been developed an entirely new science—the meteorology of the sun. Moreover, on other obscure regions of the heavens, on the physical and chemical conditions, even on the laws of the movements of the fixed and double stars, on nebulæ and milky ways, on planets and comets, on zodiacal and northern lights, has spectrum analysis thrown its enlightening rays. No less by rigorous mathematical method, through which astronomy, even at an earlier period, had been brought to a certain amount of perfection, has she in the most recent time enjoyed an unexpected triumph, by solving, through the researches of Schiaparelli, the riddle of the comets, in being able to recognize the identity of their nature with that of the swarms of shooting-stars whose remarkable brilliancy long ago made them universally known.

During the last quarter of a century, the history of the formation of our earth has assumed a new aspect. When the "Cosmos" appeared, the opinion prevailed that our earth, once a globe of liquid fire, became covered with a crust of congealed scoria?, on which, by-and-by, the first animal-and plant-life made its appearance. After an almost infinite length of time, during which the Silurian, Devonian, Carboniferous, and Permian strata were deposited, a terrible catastrophe, affecting simultaneously the whole earth, so completely destroyed the first palæozoic life, that not a single species survived the universal devastation. Upon the lifeless expanse, it was supposed, appeared then the Secondary Fauna and Flora, entirely unconnected with and different from the extinguished one, until, after frequent repetitions of the same process at longer or shorter intervals, man made his appearance, and along with him all existing plants and animals: with him begins the Historical Period, whose duration has not exceeded 6,000 years. The causes of these world-wide revolutions geology sought in the violent reaction of the molten interior against the once extremely slender crust.

In opposition to these views, the opinion peculiarly associated with the name of Lyell has made way, that no violent revolutions, returning at intervals, destroyed the external structure of the earth and all the life it sustained, but that all changes even in the earliest times affected only the earth's surface, and that these could only be the