One of the circumstances which must have helped most materially to break up the Celtic Empire was the successful revolt of the Germans against their former masters. The relation of the German to the Celtic tribes is very obscure and puzzling. The ancient Greek historians of the sixth, fifth, and fourth centuries B.C., who tell us so much about the Celts, know absolutely nothing of the Germans. As early as the year 500 B.C. Hecatæus of Miletum is able to name three peoples and two cities of India. But of the Germans, who were so much nearer to Marseilles than the nearest point of India is to the most eastern Greek colony, he says not a word. Ephorus, in the fourth century, knows of only one people to the extreme west, and they are the Celts, and their immediate neighbours are the Scythians. He knows of no intermediate state or nation. Where, then, were the Germans? The explanation lies, according to Jubainville, in this, that even before this period the German had been conquered by the Celt and become subordinated to him. The Greek historians knew of no independent state bordering upon the Scythians except the Celtic Empire alone, because none such existed. In the fifth and fourth centuries B.C., and perhaps as early as the seventh and sixth, the Germans had been subdued and had lost their independence. How and when this took place we can only conjecture, but we have philological reasons for believing that the two races had come into mutual contact at a very early date, probably as early as the eleventh century B.C. The early German name for the Rhine, for instance, _Rīno-s_, comes directly from the primitive Indo-European form _Reino-s_ and not from the Celtic _Rēno-s_, which shows that the Germans had reached that river at a time when the Celts who lived along it still called it Reinos, not Rēnos. The Celts afterwards changed the primitive _ei_ into _ē_, and from their carrying the form _réin_[18] with them into Ireland, they had probably done this as early as the ninth or tenth century B.C., for, as we have shown, the Celts who inhabited Ireland have preserved the very oldest forms of the Celtic speech. On the other hand the Celts always called that Germanic tribe who accompanied the Cimbri by the name of Teutoni, thus showing that they first came in contact with them at a date anterior to the phonetic law which introduced the so-called explosive consonants into German, and which caused the root Teutono (preserved intact by the Celts) to be turned into Theudono. From this it follows that the German and Celtic peoples were in touch with one another at a very remote period.