II. I confess that I never understood how any value could be attached to this argument. Migrations are almost universal in history, and in the traditions and legends of the new as well as of the old world. We find them among the uncivilised nations of our time, and among tribes which are still lingering in the lowest stage of savage life. With every increase and extension of knowledge, we learn to appreciate better the wandering instincts of man. Human palæontology and prehistoric archæology are daily adding their testimony to that of the historic sciences. To judge from this kind of information alone, it seems more than probable that the entire globe was peopled by means of migrations and colonisations. The primordial and uninterrupted immobility of any human race would be a fact at variance with all analogy. It would, once constituted, doubtless establish, except under exceptional circumstances, a more or less considerable number, generally the great majority of its representatives; but in the course of ages it could not fail to have cast off swarms. III. The supporters of autochthony lay especial stress upon two orders of considerations, the one drawn from the social condition of nations when still in their infancy and unprovided with the means of action which we now possess, the other from the obstacles which a hitherto invincible nature would oppose to their movements. The first objection evidently rests upon an imperfect appreciation of the aptitudes and tendencies developed in man through his different modes of life. The very imperfection of the social condition, far from arresting the diffusion of the human species, must rather have been favourable to it. Agricultural nations are of necessity settled; to pastoral nations, less bound to the soil, special conditions are indispensable. Hunters, on the contrary, by reason of their mode of life, of the necessities which it imposes, and the instincts which it develops, cannot but spread in every sense. A vast space is necessary to their existence; as soon as the numbers increase, even in a slight degree, they are forced to separate or to destroy each other, as is shown so clearly in the history of the Red-Skins. Nations of hunters and shepherds are then alone fitted for great and distant migrations. Agricultural nations are rather colonists. Ancient history itself entirely confirms these theoretical inductions. We know what the invaders of the Roman world were, the destroyers of the Eastern Empire, the Arab conquerors. The case was the same in Mexico. The Chichimequi here represent the Goths and Vandals of the Old World. If Asia has so often overrun Europe, if North America has so often sent devastating hordes into more southern regions, it is because in these two countries man was still in a barbarous or savage state.