Evidently the gravels which lie below the basalt, and interstratified with the tuffs and lavas, or below them, and which belong to an older and still more extensive denudation, must be of immense antiquity, an antiquity which remains the same whether we call it Quaternary or Tertiary. It is in these gravels that gold is found, and in the search for it great masses have been removed in which numerous stone implements have been found. The great antiquity of those gravels and volcanic tuffs is further confirmed by the changes in the flora and fauna which are proved to have occurred. The animal remains found beneath the basaltic cap are very numerous, and all of extinct species. They belong to the genera rhinoceros, elatherium, felis, canis, bos, tapirus, hipparion, elephas (primigenius), mastodon, and auchenia, and form an assemblage entirely distinct from any now living in any part of North America. Some of the genera survived into the Quaternary age as in Europe, but many, both of the genera and species, are among those most characteristic of the Pliocene period. The flora also, which is well preserved in the white clays formed from the volcanic ash, comprises forty-nine species of deciduous trees and shrubs, all distinct from those now living, without a single trace of the pines, firs, and other conifera which are now the prevalent trees throughout California. Tried by any test, therefore, of fauna, flora, and of immensely long deposit before the present drainage and configuration of the country had begun to be established, Professor Whitney's contention that the auriferous gravels are of Tertiary origin seems to be fully established. It can only be met by obliterating all definite distinction between the Quaternary and the Pliocene, and adding to the former all the time subtracted from the latter. And even if we apply this to the physical changes, it would upset all our standards of geological formations characterized by fossils, to suppose that a fauna comprising the elatherium, hipparion, and auchenia could be properly transferred to the Quaternary. In fact no one would have thought of doing so if human implements and remains had not been found in them.