But with the relics of human art, even in its most primitive stage, it is otherwise. Each example possesses an individuality of its own, for it is the product of an intelligent will, capable of development, and profiting by experience. Accumulated knowledge is the grand characteristic of man. Every age bequeaths some results of its experience; and this constitutes the vantage-ground of succeeding generations. The deterioration which follows in the wake of every impediment to such transmission and accumulation of knowledge no less essentially distinguishes man from the ingenious spinners, weavers, and builders, who require no lesson from the past, and bequeath no experience to the future. Man alone can be conceived of as an intelligent mechanician, starting with the first rudiments of art, devising tools, initiating knowledge, and accumulating experience. Whatever, therefore, tends to disclose glimpses of such a primitive condition, and of his earliest acquisitions in mechanical arts and metallurgic knowledge, helps to a just conception of primeval man. Let us then glance at the evidence we possess of such an initial stage of being. And first in seeming chronological order are those traces of human arts in the drift, or in ossiferous caves among the bones of strange orders of beings hitherto supposed to have long preceded the existence of man. In the ancient alluvial deposits—most modern among the strata of the geologist,—lie abundant traces of extinct animal life, belonging to that recent transitional era of the globe in which man first appears. In nearly all respects they present a contrast to everything we are familiar with in the history of our earth as the theatre of human action. In a zoological point of view they include man and the existing races of animals, as well as extinct races which appear to have been contemporaneous with indigenous species. To the archæologist they are rich in records of that primeval transition in which the beginnings of history lie. How early in that closing geological epoch man appeared, or how late into that archæological era the extinct fossil mammals survived, are the two independent propositions which the sister sciences have to establish and reconcile.