w, as we have seen, collected and
preserved chiefly in those public institutions which are called
archives, libraries, and museums. It is true that this does not apply to
_all_ existing documents; in spite of the unceasing acquisitions by
purchase and gift which archives, libraries, and museums all over the
world have been making every year for a long time past, there still
exist private collections, dealers who supply them, and documents in
circulation. But the exceptions, which in this case are negligeable, do
not affect the general rule. Besides, all the ancient documents which,
in limited quantity, still range at large, are destined sooner or later
to find their way into the state institutions, whose doors are always
open to let in, but never to let out.[29]

It is to be desired, as a matter of principle, that the depositories of
documents (archives, libraries, and museums) should not be too numerous;
and we have pointed out that, fortunately, they are now beyond
comparison less numerous than they were a hundred years ago. Could not
the centralisation of documents, with its evident advantages for
researchers, be carried still further? Are there not still collections
of documents of which it would be hard to justify the separate
existence? Perhaps;[30] but the problem of the centralisation of
documents is no longer urgent, now that the processes of reproduction
have been perfected, especially as the inconveniences arising from a
multitude of depositories are met by the expedient, now in general use,
of allowing the documents to travel: it is now possible for the student
to consult, without expense, in the public library of the city where he
resides, documents belonging, say, to the libraries of St. Petersburg,
Brussels, and Florence; we now rarely meet with institutions like the
Archives Nationales at Paris, the British Museum at London, and the
Mejanes Library at Aix-en-Provence, whose statutes absolutely prohibit
all lending-out of their contents.[31]

II. It being granted that the majority of historical documents are now
preserved in public institutions (archives, libraries, and museums),
Heuristic would be very easy if only good descriptive catalogues had
been drawn up of all the existing collections of documents, if these
catalogues were furnished with indexes, or if general repertories
(alphabetical, systematic, &c.) had been made relating to them; lastly,
if there were some place where it was possible to co