It is true that some eminent astronomers and physicists hesitate to accept the theory that these glacial epochs are due to the eccentricity of the earth's orbit. But the argument favoring it is well fortified and ably advanced, and if we add to the astronomical considerations involved, the physical proofs of a change in the earth's centre of gravity, caused by the excessive accumulation of ice about either pole, and the probable shifting of the Gulf stream to a southerly direction during the glacial period north, it is difficult to resist the conviction that the real cause of glaciation has been suggested in this theory. With all the ice now accumulated about the south pole transferred to the north pole, it would make an ice-cap of over thirty miles in thickness at the pole, and one sloping in all directions southward to about 60°. This accumulation, it is claimed, would so change the earth's centre of gravity as to cause all the equatorial warm waters to flow southward instead of northward, as they now do. This would certainly seem to be a most wonderful provision of nature, as well as one strongly calculated to impress the human mind with the belief that an Infinite _Pre_vision lies behind all possible _pro_vision, whether witnessed in the heavens or in the earth, in astronomical or physical phenomena. Everywhere we see infinite perfection, combined with infinite beneficence, in the adaptation of means to ends. Nothing runs to waste--all things are conserved for use. But in all the outspoken grandeur of the universe, there is nothing so grand, in exhibition at least, as the simple faith of a child, that "He who watereth the hills from his chambers," and "causeth the day-spring to know his place," will watch over the trustful little sleeper during the darkness and silence of the night. Chapter VI. The Distribution and Premanence of Species. Professor Gray, in his address before the American Association for the advancement of science, delivered at Dubuque (Ia.) in 1872, while remarking upon the wide extent of similar flora in the same plant zones, says: "If we now compare, as to their flora generally, the Atlantic United States with Japan, Mantchooria and Northern China,--_i.e._ Eastern North America with Eastern North Asia--half the earth's circumference apart, we find an astonishing similarity." But why astonishing? Had our distinguished botanical professors, in this country and in Europe, thoroughly informed themselves as to the climatic conditions, the general physical features, geographical characteristics, soil-constituents, and other conditional incidences of this Asiatic region, in the light of all the physiological facts before them, the circumstance of this great similarity of flora would have been anything but astonishing. Indeed, the astonishment, if any, would have been expressed at the want of similarity, had it been found to exist.