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Antiquity of Man: Devonian

He estimates the average thickness of the sedimentary crust of the earth to be at least one mile, and from a computhe forms they have preserved. Yet there are no fish. The Devonian age followed tranquilly and without a break, and in the Devonian sea, suddenly, fish appear, appear in shoals, and in form of the highest and most perfect type." - The Duke of Argyll, Primeval Man, p. 45, London, * T. Mellard Reade, "Limestone as an Index of Geological Time," Proceedings, Royal Society, London, vol. xxviii., p. 281. tation of the proportion of carbonate and sulphate of lime to materials held in suspension in various river-waters from a variety of formations, infers that one-tenth of this crust is calcareous.

He estimates the annual flow of water in all the great river-basins, the proportion of rain-water running off the granitic and trappean rocks, the percentage of lime in solution which they carry down, and arrives at the conclusion that the minimum time requisite for the elimination of the calcareous matter contained in the sedimentary crust of the earth, is at least six hundred millions of years.

A writer in the Gentleman's Magazine* (Professor Huxley ?), whose article I am only able to quote at second-hand, makes an estimate which, though much lower than the above, is still of enormous magnitude, as follows :- Feet.

Years.