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Page:Popular Science Monthly Volume 4.djvu/539

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THE WORLD BEFORE LIFE.

The Cherzolite, a volcanic aggregate of peridote, enstatite, and pyroxene, from the Pyrenees, in Spain, presented, after fusion, specimens the most like the meteorites. These experiments suggest that the meteors had once been fused, as is commonly believed, and that the slight differences existing between them and the peridotic rocks may be explained by supposing the latter to have cooled in the presence of oxygen (or air), while the former may have solidified where the supply of oxygen was limited. When melted, the two mixtures are precisely alike, and we may conceive of the existence beneath us, in the great caldron whence the volcanoes derive their lava, of a zone of meteor-like mixtures, both the peridotes which are now melted and occasionally brought to the surface, and the heavier metallic masses, too deeply seated to be ejected by any convulsive throb of our planet. For aught we can say, the heavier meteors may indicate the exact character of the interior nucleus, just as those black stones falling from the sky have revealed the composition of other worlds. Their weight would correspond well with that of the interior mass. The specific gravity of granite is from 2.64 to 2.76; of basalt, 2.9 to 3:1; the peridotes, 3.3 to 3.44; and the heavy meteors from 7 to 8. Hence, while the granitic

Fig. 5.
PSM V04 D539 Zones in the earth and atmosphere.jpg
Zones in the Earth and Atmosphere.

A. Solid Nucleus of Heavy Metals or Meteors; B. Region of Stony Meteors; C. Region of Lava; D. Region of Basalt and Pophyry; E. Region of Granite, and Surface of the Solid Crust; P. Region of Acid Gases; G. Region of Carbonic Acid; H. Region of Nitrogen and Oxygen; I. Steam.

materials may have cooled near the surface, and the basalts lower down, the stony meteors would form a zone beneath the second, and the metallic masses, if present, may constitute the central nucleus. We must not forget the trachytes, and most modern lavas, which would underlie the basalts. It would be easy to calculate the thickness required for these different zones, whose general average should be the density of the earth. When water is added to the peridotes and stone-meteorites, the rock is analogous to serpentine. We may