[51] This is a suitable place to enumerate the principal "manuals" published in the last twenty-five years. But a list of them, ending at 1894, will be found in Bernheim's _Lehrbuch_, pp. 206 sqq. We will only refer to the great "manuals" of "Philology" (in the comprehensive sense of the German "Philologie," which includes the history of language and literature, epigraphy, palæography, and all that pertains to textual criticism) now in course of publication: the _Grundriss far indo-arischen Philologie und Altertumskunde_, edited by G. Bühler; the _Grundriss der iranischen Philologie_, edited by W. Geiger and E. Kuhn; the _Handbuch der classichen Altertumswissenschaft_, edited by I. von Müller; the _Grundriss der germanischen Philologie_, edited by H. Paul, the second edition of which began to appear in 1896; the _Grundriss der romanischen Philologie_, edited y G. Gröber. In these vast repertories there will be found, along with a short presentment of the subject, complete bibliographical references, direct as well as indirect. [52] The French "manuals" of MM. Prou (Palæography), Giry (Diplomatic), Cagnat (Latin Epigraphy), and others, have diffused among the public the idea and knowledge of the auxiliary subjects of study. New editions have enabled, and will enable, them to be kept up to date--a very necessary operation, for most of these subjects, though now settled in the main, are being enriched and made more precise every day. Cf. _supra_, p. 38. [53] What exactly are we to understand by this "incommunicable knowledge," of which we speak? When a specialist is very familiar with the documents of a given class or period, associations of ideas are formed in his brain; and when he examines a new document of the same class or species, analogies suddenly dawn upon him which would escape any one of less experience, however well furnished he might be with the most perfect repertories. The fact is, that not all the peculiarities of documents can be isolated; there are some which cannot be classified under any intelligible head, and which, therefore, cannot be found in any tabulated list. But the human memory, when it is good, retains the impression of these peculiarities, and even a faint and distant stimulus suffices to revive the apprehension of them. [54] _Supra_, p. 17. [55] This expression, which frequently occurs, needs explanation. It is not to be taken to apply to a _species_ of facts. There are no historical facts in the sense in which we speak of chemical facts. The same fact is or is not historical according to the manner in which it is known. It is only the mode of acquiring knowledge that is historical. A sitting of the Senate is a fact of direct observation for one who takes part in it; it becomes historical for the man who reads about it in a report. The eruption of Vesuvius in the time of Pliny is a geological fact which is known historically. The historical character is not in the facts, but in the manner of knowing them.