and meaning may differ together to any extent, and yet the words may be one and the same, and good evidences of relationship between the languages to which they respectively belong. Not literal agreement, but such resemblances, nearer or more distant, clearer or more obscure, as are proved by supporting facts to have their ground in original identity, make satisfactory evidence of common descent in language.
Here, then, is the practical difficulty in the way of him who would prove all human speech a unit. On the one hand, those fortuitous coincidences and analogies which any given language may present with any other with which it is compared form a not inconsiderable body, an appreciable percentage of its general stock of words. On the other hand, the historical coincidences and analogies traceable between two languages of common descent are capable of sinking to as low, or even to a lower, percentage of its vocabulary. That is to say, there may be two related tongues, the genuine signs of whose relationship shall be less numerous and conspicuous than the apparent but delusive signs of relationship of two others which derive themselves from independent origins. The former have been so long separated from one another, their changes in the mean time have been so pervading, that their inherited points of resemblance are reduced in number and obscured in character, until they are no longer sufficient to create a reasonable presumption in favour of their own historical reality; they are undistinguishable from the possible results of chance. As we saw in the sixth lecture (p. 243), evidences of genetic connection are cumulative in their character; no single item of correspondence is worth anything until there are found kindred facts to support it; and its force is strengthened with every new accession. And, in the comparison of languages, the point is actually reached where it becomes impossible to tell whether the few coincidences which we discover are the genuine traces of a community of linguistic tradition, or only accidental, and evidence of nothing. When we come to holding together the forms of speech belonging to the diverse families, linguistic testimony fails us: it no longer has force to prove anything to our satisfaction.
