Page:The Last link.djvu/150

138 Tertiary period has by the same authorities been fixed approximately at 3,000,000 to 4,000,000 years. Beyond this we cannot venture without the wildest speculation; but we know to a certain extent the thickness of the various sedimentary strata, which amount in all to from 100,000 to 175,000 feet—on the average perhaps 130,000 feet, or about twenty miles.

Unless we prefer giving up all attempt at calculation as absolutely hopeless, and thus resign the whole problem, we must at least try to arrive at some results, and then see if these cannot reasonably be made use of.

Neither geologist nor physicist, and no zoologist, would accept the suggestion that these 130,000 feet of stratified rocks have been deposited within only as many years, although the average rate of deposit would in that case be not more than 1 foot per year. On the other hand, an indignant protest is raised against the assumption of 1,000,000,000 years.