h "manuals" of MM. Prou (Palaeography), 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.

[56] Fustel de Coulanges has said it. Cf. _supra_, p. 4, note 1.

[57] In the sciences of observation it is the fact itself, observed
directly, which is the starting-point.

[58] _Infra_, ch. vii.

[59] We shall not treat specially of the criticism of material documents
(objects, monuments, &c.) where it differs from the criticism of written
documents.

[60] For the details and the logical justification of this method see
Seignobos, _Les Conditions psychologiques de la connaissance en
histoire_, in the _Revue phi