No doubt the temperature was really lower at the quaternary age and at the epoch generally assigned to man's advent in European countries, but the difference was not so great as some say. A lowering of four degrees is sufficient to explain the ancient extension of the glaciers. We can look on this figure as the maximum, for it is proved to-day that humanity played the main _role_ in the glacial phenomena. The beds of rivers and the alluvia are there to tell that all the water was not in a solid state at that time, that the glaciers were much more extended than in our days, and that the courses of the rivers were infinitely more abundant. When this is understood we can reasonably reduce the extension of the ancient glaciers, the lowering of the temperature at the quaternary age, and account for the uninterrupted life of the fauna and flora. However, we must not fall into the opposite excess and assert, as some have done, that the glacial period is comparatively recent, the traces of which are too plain and fresh in some localities to assign to it an age prior to man, and that the temperature has rather lowered itself since this epoch. The ancient extension of the glaciers has been followed by a corresponding growth and extension of animal life, thus proving that the permanence of glaciers is a wise provision and absolutely essential to man and the high orders of animals and vegetation. The ancient extension does not prove alone that it was much colder than in historic times, for the animals themselves are proof of this. At that time the plains of Europe, and of France in particular, were animated by herds of reindeer, gluttons, camels, and marmots, which one does not find to-day except in the higher latitudes or more considerable heights. The mammoth and rhinoceros are no exception to this, for naturalists know they were organized to live in cold countries. Space will not permit us to pursue this point further, or speculate on the probable climatic conditions of the ice age; but we can carry ourselves back a few thousand years and describe the climate of Europe and neighboring countries of Africa and Asia. Herodotus describes the climate of Scythia in terms which would indicate in our day the countries of Lapland and Greenland. He shows us the country completely frozen during eight months of the year; the Black Sea frozen up so that it bore the heaviest loads; the region of the Danube buried under snow for eight months, and watered in summer by the abundant rains which gave to the river its violent course. The historian adds that the ass cannot live in Scythia on account of the extreme cold which reigns there. The following century Aristotle makes the same remarks concerning Gaul. His contemporary, Theophrastes, tells us that the olive tree did not succeed in Greece more than five hundred furlongs from the sea. We can assure ourselves that both the ass and the olive thrive in these countries at the present day.