But we must not expect that we shall be able, in the existing state of knowledge, to trace this continuity from first to last, for the links that are lost far exceed in number those which remain. The task may be compared to that of putting together the fragments of a tree that has been cut up for firewood, and of which the greater part has been burnt. It is only here and there, after diligent search, that we may expect to find a few pieces fitting in such a manner as to prove that they belonged to the same branch. We do not, on that account, abandon our conviction that the tree once grew, that every large branch was once a small twig, and that every limb developed by a natural process into the form in which we find it. The difficulty we have to contend with is precisely that which the geologist experiences in tracing his palaeontological sequence. But it is far greater, for natural history has been long studied, and the materials upon which Mr. Darwin founds his celebrated hypothesis have been in process of collection for many generations. But continuity, in relation to the arts, can scarcely yet be said to be established as a science. The materials for the science have not yet been even classified, and classification is a process which must always precede continuity in the study of nature. Classification defines the margin of our ignorance; continuity results from the extension of knowledge, by bridging over the distinction of classes. Travellers, for the most part, have been in the habit of bringing home, as curiosities, the most remarkable specimens of weapons and implements, without much regard to their history or the evidence they convey; and their descriptions of them, as a general rule, have been extremely meagre. Until quite recently, the curators of our ethnographical museums have aimed more at the collection of unique specimens, serving to exhibit well-marked differences of form, than such as by their resemblance enable us to trace out community of origin. The arrangement of them has been almost universally bad, and has been calculated rather to display the several articles to advantage, on the principle of shop windows, than to facilitate the deductions of science. The antiquities of savage races, moreover, have as yet been almost wholly unstudied.