enjoys the advantage of access to the parent tongue itself, from which the more recent idioms are almost bodily derived: thus, for example, our possession of the Latin gives to our readings of the history of the Romanic tongues, our determination of the laws which have governed their growth, a vastly higher degree of definiteness and certainty than we could reach if we only knew that such a parent tongue must have existed, and had to restore its forms by careful comparison and deduction. Next in value to this is the advantage of commanding a rich body of older and younger dialects of the same lineage, wherein the common speech is beheld at nearer and remoter distances from its source, so that we can discover the direction of its currents, and fill out with less of uncertainty those parts of their network of which the record is obliterated. This secondary advantage we enjoy in the Germanic, the Persian, the Indian branches of Indo-European speech; and, among the grander divisions of human language, we enjoy it to an extent elsewhere unapproached in the Indo-European family, that immense and varied body of allied forms of speech, whose lines of historic development are seen to cover a period of between three and four thousand years, as they converge toward a meeting in a yet remoter past.
Herein lies the sufficient explanation of that intimate connection, that almost coincidence, which we have noticed between the development of Indo-European comparative philology and that of the general science of language. In order to comprehend human language in every part, the student would wish to have its whole growth, in all its divisions and subdivisions; through all its phases, laid before him for inspection in full authentic documents. Since, however, anything like this is impossible, he has done the best that lay within his power: he has thrown himself into that department of speech which had the largest share of its history thus illustrated, and by studying that has tried to learn how to deal with the yet more scanty and fragmentary materials presented him in other departments. Here could be formed the desired nucleus of a science; here the general laws of linguistic life could be discovered; here could be worked