The upper waters of the Rio Frio and its affluents form the locality of the _Guatusos_ or Huatusos. By some older writers these were supposed to be of Nahuatl affinities, and others said that they were “white Indians.” Neither of these tales has any foundation. I have seen some of the Guatusos, and their color is about that of the average northern Indians; and as for their language, of which we have rather full vocabularies, it is not in the slightest related to the Nahuatl, but is an independent stock. They are a robust and agile set, preferring a wild life, but cultivating maize, bananas, tobacco and other vegetables, and knitting nets and hammocks from the fibres of the agave. The huleros, or gatherers of india rubber, persecute them cruelly, and are correspondingly hated. It is doubtful if at present they number over six hundred.[217] The mountain chain which separates Nicaragua from Costa Rica, and the head-waters of the Rio Frio from those of the more southern and eastern streams, is the ethnographic boundary of North America. Beyond it we come upon tribes whose linguistic affinities point towards the southern continent. Such are the Talamancas, Guaymies, Valientes and others, which I must include, in view of recent researches into their languages, in the next section. SOUTH AMERICAN TRIBES. GENERAL REMARKS. The linguistic classification of the South American tribes offers far greater difficulties than that of North America. Not only has it been studied less diligently, but the geographical character of the interior, the facilities with which tribes move along its extensive water-ways, and the less stable temperament of the white population have combined to obscure the relationship of the native tribes and to limit our knowledge about them. The first serious attempt to take a comprehensive survey of the idioms of this portion of the continent was that of the Abbé Hervas in his general work on the languages of the globe.[218] Balbi and Adelung did scarcely more than pursue the lines he had traced in this portion of the field. So little had these obtained definite results that Alexander von Humboldt renounced as impracticable the arrangement of South American tribes by their languages, because “more than seven-eighths would have remained what the classifying botanists call _incertæ sedis_.”[219] This eminent naturalist, however, overlooked no opportunity to collect material for the study of the native tongues, and on his return to Europe placed what he had secured in the hands of his distinguished brother for analysis. William von Humboldt, who was the profoundest linguist of his day, gave close attention to the subject, but rather from a purely critical than an ethnographic aspect. He based upon the South American languages many principles of his linguistic philosophy; but so little general attention was given the subject that his most valuable study was first given to the press by myself in 1885.[220]