E. 66–72. Applications of genealogy
66. After this brief sketch of the modes of discovering genealogical facts by means of the extant texts, which will, we hope, be made clearer by the concrete examples to be given further on, we come to the uses of the facts so obtained for the discrimination of true from false readings. One case of the examples given in § 51 shews at once that any number of documents ascertained to be all exclusively descended from another extant document may be safely put out of sight, and with them of course all readings which have no other authority. The evidence for the fact of descent may be of various kinds. Sometimes, though rarely, it is external. Sometimes it consists in the repetition of physical defects manifestly not antecedent to the supposed original, as when the loss of one or more of its leaves has caused the absence of the corresponding portions of text in all the other documents. Sometimes the evidence is strictly internal, being furnished by analysis of the texts themselves, when it is found that a fair number of mere blunders or other evidently individual peculiarities of the supposed original have been either reproduced or patched up in all the supposed derivative documents, and secondly that these documents contain few or no variations from the text of the supposed original which cannot be accounted for by natural and known causes of corruption.
67. This summary reduction of documentary evidence by the discovery of extant ancestors of other existing documents is however of rare occurrence. On the other hand, wherever a text is found in a plurality of documents, there is a strong probability that some of them are descended from a single lost original. The proof of com-
