ethnico-linguistic differences, the tribes about the head-waters of the Xingu present complete uniformity in their daily habits, in the conditions of their existence, and their general culture[771]," though it is curious to note that the art of making pottery is restricted here to the Arawak tribes[772]. Yet amongst them are represented three of the radically distinct linguistic groups of Brazil, some (Bakairi and Nahuqua) belonging to the Carib, some (Auetoe and Kamayura) to the Tupi-Guarani, and some (Mehinaku and Vaura) to the Arawak family. Obviously these could not be so discriminated but for their linguistic differences. On the other hand the opposite phenomenon is occasionally presented of tribes differing considerably in their social relations, which are nevertheless of the same origin, or, what is regarded by Ehrenreich as the same thing, belong to the same linguistic group. Such are the Ipurina, the Paumari and the Yamamadi of the Purus valley, all grouped as Arawaks because they speak dialects of the Arawakan stock language. At the same time it should be noted that the social differences observed by some modern travellers are often due to the ever-increasing contact with the whites, who are now encroaching on the Gran Chaco plains, and ascending every Amazonian tributary in quest of rubber and the other natural produce abounding in these regions. The consequent displacement of tribes is discussed by G. E. Church[773]. In the introduction to his valuable list Clements Markham observes that the evidence of language favours the theory that the Amazonian tribes, "now like the sands on the sea-shore for number, originally sprang from two or at most three parent stocks. Dialects of the _Tupi_ language extend from the roots of the Andes to the Atlantic, and southward into Paraguay ... and it is established that the differences in the roots, between the numerous Amazonian languages, are not so great as was generally supposed[774]." This no doubt is true, and will account for much. But when we see it here recorded that of the Carabuyanas (Japura river) there are or were 16 branches, that the Chiquito group (Bolivia) comprises 40 tribes speaking "seven different languages"; that of the Juris (Upper Amazons) there are ten divisions; of the Moxos (Beni and Mamore rivers) 26 branches, "speaking nine or, according to Southey, thirteen languages"; of the Uaupes (Rio Negro) 30 divisions, and so on, we feel how much there is still left to be accounted for. Attempts have been made to weaken the force of the linguistic argument by the assumption, at one time much in favour, that the American tongues are of a somewhat evanescent nature, in an unstable condition, often changing their form and structure within a few generations. But, says Powell, "this widely spread opinion does not find warrant in the facts discovered in the course of this research. The author has everywhere been impressed with the fact that savage tongues are singularly