that, if there was an ancient common source of several modern languages, they have become so much differentiated, that without historical knowledge of their growth, the attempts to prove their interrelation cannot succeed.
It should be borne in mind that the problem of the study of languages is not one of classification but that our task is to trace the history of the development of human speech. Therefore, classification is only a means to an end. Our aim is to unravel the history of the growth of human language, and, if possible, to discover its underlying psychological and physiological causes. From this point of view the linguistic phenomena cannot be treated as a unit, but the manifestations of linguistic activity must be studied first each by itself, then in their relations to other linguistic phenomena.
The three fundamental aspects of human speech are phonetics, grammar, and vocabulary. When we turn to their consideration separately, we find, at least in America, a curious condition. The study of phonetics indicates that certain features have a limited and well-defined distribution which, on the whole, is continuous. To give an example: the extraordinary development of the series of k sounds and of laterals (l sounds) is common to the most diverse languages of the North Pacific coast, while in California and east of the Rocky mountains this characteristic feature disappears. In a similar way nasalization of vowels is absent in the northwest part of America, but it is very strongly developed on the central and eastern plains. The labialization of k sounds following an o or u is widely spread in the extreme Northwest, and infrequent outside of that territory. The study of the phonetics of America is not sufficiently developed to describe in detail areas of distribution of characteristic sounds or sound groups, but it may safely be stated from what we know, that similar phonetic traits often belong to languages which are morphologically entirely distinct; and that on the other hand, very great phonetic differences develop in the same linguistic stock.
The study of the morphology of American languages illustrates also definite areas of characterization. It is, for instance, most
