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482 the different caves. Had the conditions in all cases been the same, there can be no doubt that any marked variations in the fauna of the same region would afford valuable criteria for determining such a chronological sequence. But such decided differences cannot at present be traced; and inasmuch as the animal remains in the caverns under consideration have, almost without exception, been introduced into the caves by human agency, and been merely the refuse of the spoils of the chase consumed by the old cave-dwellers, we may readily conceive reasons why, without any great natural change in the fauna, the proportionate numbers of the different animals eaten during a certain number of years might vary in different caves. Still the effect of human agency in causing an alteration in the larger mammalian fauna of a district is great, and of this, researches in caverns may probably afford evidence.

Dr. E. Dupont has adopted a somewhat similar, but more limited, and therefore safer view with regard to the caverns of Belgium, and has moreover correlated the cave-deposits with those of wider range. The rolled pebbles and stratified clay of the river-valleys he regards as synchronous with the deposits in certain caves belonging to what he terms the Mammoth Period; and the angular gravels and brick-earth, of somewhat later date, he connects with the caves of the Reindeer Period.

As will shortly be seen, there appears good reason for regarding the two sets of caverns thus characterized, as belonging to different ages; and if the use of the terms Mammoth and Rein- deer Periods be not supposed to limit the duration of the existence of those animals in France and Belgium to so short a space of time, geologically speaking, as that represented by the infilling of each set of caves, no harm can arise from the adoption of the terms.

Under any circumstances, with our present knowledge, there seems a sufficient variation in the proportion of the different animals one to the other, and also in the character of the implements in different caves, to justify the conclusion that the cave-remains of Western Europe are memorials, not of some comparatively short Troglodyte phase of the human race, but of a lengthened chapter in its history. And yet this chapter seems to have been completely closed before the implements belonging to the Neolithic or Surface Stone Period had come into use; for though these also