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Show The Krtli' Age. The age of the earth is estimated from the increment in tho temjK raturo as wa IH'iietrate its crust. The r;ita at which tho earth cools can only bo determined by making use of data confessedly im-jM'rfeet; im-jM'rfeet; but from theso Sir William Thompson fuids that 100,000,000 or 200,-000,000 200,-000,000 years ago it first began to be crusted over by a solid film of rockn; that 10,000,000 years afterward it wad j still so hot that tho temperature increased in-creased 2 degs. Fahrenheit for every foot vertically descended below tho zone of constant temperature Tho present rate of increase averages abont 1.51 of a degree de-gree for every foot. St. Lonis Republic, |