Thus within the historic period, as in prior geological eras, the progress of time is recorded by the extinction of races. The advent of man was speedily marked by the disappearance of numerous groups of ancient life which pertain to that transitional era where archæology begins; though the most recent discoveries of works of art along with the fossil mammals of the drift, confirm, by new and striking evidence, the fact that man entered on this terrestrial stage, not as the highest in an entirely new order of creation, and belonging to an epoch detached by some overwhelming catastrophe from all preceding periods of organic life: but as the last and best of an order of animated beings whose line sweeps back into the shadows of an unmeasured past. The disclosures of British tumuli, along with rarer chance deposits, show that the Celtic Briton was an intruder upon older allophylian occupants; while the presence of the Roman is recorded for us by the extinction of an ancient fauna, as well as of whole British tribes. What the Roman partially accomplished, the Saxon, the Dane, and the Norman completed: displacing the Briton everywhere but from the fastnesses of Wales; and gradually extirpating all but such animals as are either compatible with the development of social refinement, or are worthy of protection as a means of ministering to man’s pleasures. And as it has been in the Old World, so it is in the New. The progress of the European colonists not only involves the extirpation alike of the wild animals and the forests which formed their haunts; but also the no less inevitable disappearance of the aborigines who made of them a prey. Thus the grave-mound of the Red Indian, and the relics of his simple arts, become the memorials of an extinct order of things no less clearly defined than the post-tertiary fossils of the drift.