Throughout the successive geologic strata of earthy matter that overlie the solid rocky foundations below, traces of man's presence are found. It is in deposits of peat and alluvium that these traces are most clearly defined and with greatest facility studied. The extremely slow accumulation of these deposits and the great depth at which human remains appear, impress the mind of the observer with a vivid idea of their antiquity. Calculations based on the known rate of increase for a definite period fix the age of the lowest relics at from six thousand to one hundred thousand years according to the locality. But geology tells yet no definite tale in years, her chronology being on a grander scale, and these calculations are to scientific men the weakest proofs of man's antiquity. As we penetrate, however, this superficial geologic formation, we find in the upper layers weapons and implements of iron; then, at a greater depth, of bronze; and lowest of all stone is the only durable material employed. In all parts of the world, so far as explorations have been made, this order of the ages, stone, bronze, iron, is observed; although they were certainly not contemporaneous in all regions. With the products of human skill, in its varying stages of development, are mingled the fossil trees and plants of different species which flourished and became locally extinct as the centuries passed away. So animal remains, no less abundant than the others, indicate successive changes in the fauna and its relations to human life, the animals pursued at different epochs for food, the introduction of domestic animals, and the transition from the chase to agriculture as a means of subsistence.