In attacking the question of Tertiary man, the first point is to aim at some clear conception of where the Pliocene ends and the Quaternary begins. These are after all but terms applied to gradual changes through long intervals of time; still they require some definition, or otherwise we should be beating the air, and ticketing in some museums as Tertiary the identical specimens which in others were labelled as Quaternary. This turns very much on whether the first great glaciation was Pliocene or Quaternary, and must be decided partly by the order of superposition and partly by the fauna. If we can find a section where a thick morainic deposit is interposed between two stratified deposits, a lower one characterized by the usual fauna of the Older Pliocene, and an upper one by that of the Newer Pliocene, it is evident that the glacier or ice-cap which left this moraine must have existed in Pliocene times. We know that the climate became colder in the Pliocene, and rapidly colder towards its close, and that in the cliffs of Cromer, the forest bed with a temperate climate had given place to Arctic willows and mosses, before the first and lowest boulder-clay had brought blocks of Scandinavian granite to England. We should be prepared, therefore, for evidence that this first period of greatest cold had occurred within the limits of the Pliocene period. Such evidence is afforded by the valleys which radiate from the great central boss of France in the Auvergne. The hill of Perrier had long been known as a rich site of the fossil remains of the extinct Pliocene fauna, and its section has been carefully studied by some of the best French geologists, whose results are summed up as follows by Hamy in his _Palæontologie humaine_-- "The bed-rock is primitive protogine, which is covered by nearly horizontal lacustrine Miocene, itself covered by some metres of fluviatile gravels. Above comes a bed of fine sand, a mètre thick, which contains numerous specimens of the well-known mammalian fauna of the Lower Pliocene, characterized by two mastodons (_M. Armenicus_ and _M. Borsoni_). Then comes a mass of conglomerates 150 mètres thick, consisting of pebbles and boulders cemented by yellowish mud; and above this a distinct layer of Upper Pliocene characterized by the _Elephas Meridionalis_.