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THE JOURNAL OF GEOLOGY.

I believe can be removed; but others perhaps cannot in the present condition of science, and may indeed eventually prove fatal. Time alone can show. I state briefly some of these objections.

1. Mathematical physicists assure us that on any reasonable premises of initial temperature and rate of cooling of the earth, the amount of lateral thrust produced by interior contraction would be wholly insufficient to account for the enormous foldings.[1] Let us admit—surely a large admission—that this is so. But this conclusion rests on the supposition that the whole cause of interior contraction is cooling. There may be other causes of contraction. If cooling be insufficient, our first duty is to look for other causes. Osmund Fisher has thrown out the suggestion (a suggestion by the way highly commended by Herschel) that the enormous quantity of water vapors ejected by volcanoes and the probable cause of eruptions is not meteoric in origin as generally supposed, but is original and constituent water occluded in the interior Magma.[2] Tschermak has connected this escape of constituent water from the earth with the gaseous explosions of the sun.[3] Is it not barely possible that we may have in this an additional cause of contraction, more powerfully operative in early times but still continuing? See the large quantity of water occluded in fused lavas to be "spit out" in an act of solidification! But much still remains in volcanic glass which by refusion intumesces into lightest froth. Here then, is a second possible cause of contraction. If these two be still insufficient, we must look for still other causes before rejecting the theory.

2. Again: Dutton[4] has shown that in a rigid earth it is impossible that the effects of interior contraction should be concentrated along certain lines so as to form mountain ranges, because this would require a shearing of the crust on the interior. The yield-

  1. ↑ Cam. Phil. Trans. Vol. XII., Part II., Dec. 1873.
  2. ↑ Cambridge Phil. Trans. Vol. XII., Part II., Feb. 1875.Physics of the Earth's Crust, p. 87.
  3. ↑ Geol. Mag. Vol. IV., p. 569, 1877.
  4. ↑ Am. Jour. Vol. VIII., p. 13, 1874.Penn. Monthly, May, 1876.
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