incandescent bodies. Geology gives abundant proof of igneous action in our globe at a former period, and we have reason to believe that we now stand on a crust floating on a molten sea. When we look to the moon J we find innumerable extinct volcanoes, like so many furnaces in an iron district, put out by a general strike. The other planets do not allow us to see their minuter features, but analogy fairly leads to the conclusion that they were all, at one time, active furnaces.
The concentric envelopes of the sun are, by no means, a distinctive feature, or one that should separate it from the family of planets. The rings of Saturn are* only a special case of this concentricity — the ring being merely a flattened sphere. The envelopes of the sun are somewhat flattened, and Saturn's rings are only an extreme case. The spherical mop, when twirled, becomes a flat ring, so that the mere circumstance of motion explains the difference. The sun has, indeed, rings similar to those of Saturn. We have seen that the zodiacal light, and the zones of asteroids and meteorites are analogous to these rings. The earth also afl'ords an example of the concentric structure. In an eclipse of the moon, an inhabitant of that body would behold a spectacle similar to what is presented in a solar eclipse. He would see a faint corona, and, along the margin of the earth, he would see a copper-coloured stratum, with prominences like the rose-coloured shell of the sun, this stratum being
