date for the common original of these various generations of descendants, the later of which are themselves early. Nothing of course can exclude the possibility that one line of transmission may have ramified more rapidly and widely than another in the same time: yet still the shorter the interval between the time of the autograph and the end of the period of transmission in question, the stronger will be the presumption that earlier date implies greater purity of text. But the surest ground of trusting composite attestation is attained when it combines the best documentary representatives of those lines of transmission which, as far as our knowledge goes, were the earliest to diverge. Such are essentially instances of ascertained concordance of X and Υ (§ 69), in spite of the dissent of some descendants of one or both.
76. The limitation to "the best documentary representatives" is necessary, because the intrusion of mixture in documents, or in lost originals of documents or of documentary groups, may disguise the actual historical relations (see § 61), and give the appearance of greater compositeness of attestation to readings which have merely invaded lines of transmission that for a while were free from them. It thus becomes specially necessary to observe which documents, or lost originals of documents or documentary groups, are found to shew frequent or occasional mixture with texts alien from their own primary ancestry, and to allow for the contingency accordingly. Many cases however of ambiguous interpretation of evidence are sure to remain, which the existing knowledge of the history of mixture is incompetent to clear up; and for these recourse must be had to evidence of other kinds.
