obvious natural pantomime, and those proving efficient to convey most successfully at any time the several ideas became the most widely adopted, liable, however, to be superseded by more appropriate conceptions and delineations.  The skill of any tribe and the copiousness of its signs are proportioned first to the necessity for their use, and secondly to the accidental ability of the individuals in it who act as custodians and teachers, so that the several tribes at different times vary in their degree of proficiency, and therefore both the precise mode of semiotic expression and the amount of its general use are always fluctuating.  Sign language as a product of evolution has been developed rather than invented, and yet it seems probable that each of the separate signs, like the several steps that lead to any true invention, had a definite origin arising out of some appropriate occasion, and the same sign may in this manner have had many independent origins due to identity in the circumstances, or if lost, may have been reproduced.

The process is precisely the same as that observed among deaf-mutes.  One of those unfortunate persons, living with his speaking relatives, may invent signs which the latter are taught to understand, though strangers sometimes will not, because they may be by no means the fittest expressions.  Should a dozen or more deaf-mutes, possessed only of such crude signs, come together, they will be able at first to communicate only on a few common subjects, but the number of those and the general scope of expression will be continually enlarged.  Each one commences with his own conception and his own presentment of it, but the universality of the medium used makes it sooner or later understood.  This independent development, thus creating diversity, often renders the first interchange of thought between strangers slow, for the signs must be self-interpreting.  There can be no natural universal language which is absolute and arbitrary.  When used without convention, as sign language alone of all modes of utterance can be, it must be tentative, experimental, and flexible.  The mutes will also resort to the invention of new signs for new ideas as they arise, which will be made intelligible, if necessary, through the illustration and definition given by signs formerly adopted, so that the fittest signs will be evolved, after rivalry and trial, and will survive.  But there may not always be such a preponderance of fitness that all but one of the rival signs shall die out, and some, being equal in value to express the same idea or object, will continue to be used indifferently, or as a matter of individual taste, without confusion.  A multiplication of the numbers confined together, either of deaf-mutes or of Indians whose speech is diverse, will not decrease the resulting uniformity, though it will increase both the copiousness and the precision of the vocabulary.  The Indian use of signs, though maintained by linguistic diversities, is not coincident with any linguistic boundaries.  The tendency is to their uniformity among groups of people who from any cause are brought into contact with each other while still speaking different languages.  The longer and closer such contact, while no common tongue is adopted, the greater will be the uniformity of signs.