Page:A Treatise on Geology, volume 1.djvu/27

 CHAP. I. beyond the date of the present surface. The series of strata is so ancient, that even its uppermost and newest term in every country is older than the race of man now existing there; though we are not entitled to say, without further examination, that it is older than the human species generally, for it is supposable that a former race of men might have existed over an older surface of the same part of the spherical area, under older physical conditions.

The records and traditions of mankind, which give a few thousand years to the existence of the human species on the globe under its present physical conditions, are in some respects corroborated by geological evidence of the comparatively recent date at which atmospheric agencies and drainage waters began to waste the surface of the earth, under the present relations of the level of land and sea. The notices of Herodotus concerning the formation of the alluvial land in Egypt from the inundations of the Nile, and similar facts connected with other great rivers, combine with the elaborate arguments of De Luc, concerning the formation of deltas in the upper ends of lakes, instances of which abound in every country, to show that the actual relations of the level of land and sea are, for the most part, not of so ancient a date as to be beyond comparison with the traditionary dates of the antiquity of the human race.

Having thus adopted as the limit of least antiquity of the scale of stratified rocks, the traditionary age of the human race, let us turn to consider the nature and meaning of the scale itself, so as to learn its value and range in the interpretation of the phenomena which happened in earlier physical conditions of the globe.