Of Paradise, when all the holy streams Of the lone outcasts quailed before its glare, And men are gazing to these "signs in Heaven" Beleaguer'd by the Roman,- when the skies Oh, God of mystery! these fires are thine! In starry language, visible to all, Of the down looking spirits of the earth! Where the ice mountains hem the frozen pole, Alas! for us who boast of deeper lore, PART III. PHYSICAL STRUCTURE OF THE EARTH. CHAPTER 1. Structure of the Earth. "Ye mighty ones who sway the souls that go Ye, silent shades, who sit and hear around! Virgil. We have before shown that our globe is a planetary orb of a few thousand miles in diameter, and of a spheroidal shape, the difference between the polar, and equatorial diameters being twenty-six miles. The mean density of the earth, is about five times that of water, the interior being double that of the solid su perficial crust, hence if the interior of the earth be cavernous, its crust must be composed of very dense materials. The crust, or outer covering of the earth, significantly called “ Erdrinde," or Earth-rind, by the Germans, is that part to which our investigations are naturally directed. The greatest thickness of this superficial crust, which man has been able to explore, estimated from the highest mountain peaks, to the greatest natural or artificial depths, does not exceed ten miles; this, in comparison with the diameter, 8000 miles, is a distance, utterly insignificant, bear ing about the same relative proportion, as the thickness of this paper to an artificial sphere a foot in diameter. The inequalities and crevices in the varnish of such a sphere, would proportionately represent the highest mountains, and deepest valleys. In the following diagram, from the Penny Cyclopedia, the relative proportions of the crust of the earth, and the inequalities of its surface, as compared with the mass of our planet, are attempted to be shown. The line from e to k, represents a depth of 500 miles, to the point i, a depth of 100 miles, and to the line b, 45 miles above the surface, the supposed limit of the earth's atmosphere. The dark line represents a thickness of ten miles, the estimated thickness of the crust of the earth; the points de ƒ g, indicate the altitudes of the highest mountains in the world. The highest peak in Europe, being Mont Blanc, which is 15,660 feet above the level of the sea; and in America, Mount Sorata, Andes, 25,400 feet, and in Asia, Chumularee, Himalayah, estimated at 29,000 feet, being more than five miles of perpendicular altitude. The depth of the sea is shown by the line a h, at the extremity of the arc. When we consider that the altitude of the highest mountains bears so small a proportion to the probable thickness of the earth's crust, we will be prepared to admit the possibility that they might once have been the bed of the ocean, and may have been raised to their present situations by subterranean agency, |