The second migration of the Aryan race is supposed to have been that of the Celtic tribes, who took a more northerly course, by way of the steppes of the Volga and the Don, and gradually obtained possession of all Central and Western Europe, including the British Isles. Their advance was only stopped by the ocean, and the tribe which first appears in history, the Gauls, was at that time beginning to move eastward again, in search of new fields of plunder. It is impossible to ascertain whether the German tribes immediately followed the Celts, and took possession of the territory which they vacated in pushing westward, or whether they formed a third migration, at a later date. We only know the order in which they were settled when our first historical knowledge of them begins. In the fourth century before the Christian Era, all Europe west of the Rhine, and as far south as the Po, was Celtic; between the Rhine and the Vistula, including Denmark and southern Sweden, the tribes were Germanic; while the Slavonic branch seems to have already made its appearance in what is now Southern Russia. Each of these three branches of the Aryan race was divided into many smaller tribes, some of which, left behind in the march from Asia, or separated by internal wars, formed little communities, like islands, in the midst of territory belonging to other branches of the race. The boundaries, also, were never very distinctly drawn: the tribes were restless and nomadic, not yet attached to the soil, and many of them moved through or across each other, so that some were constantly disappearing, and others forming under new names. [Sidenote: 113 B. C. THE CIMBRIANS AND TEUTONS.] The Romans first heard the name "Germans" from the Celtic Gauls, in whose language it meant simply _neighbors_. The first notice of a Germanic tribe was given to the world by the Greek navigator Pytheas, who made a voyage to the Baltic in the year 330 B. C. Beyond the amber-coast, eastward of the mouth of the Vistula, he found the Goths, of whom we hear nothing more until they appear, several centuries later, on the northern shore of the Black Sea. For more than two hundred years there is no further mention of the Germanic races; then, most unexpectedly, the Romans were called upon to make their personal acquaintance.