ch
we have endeavoured to expand.[43] The expanded sketch bears date April
1896: numerous additions, not to speak of revision, would already be
necessary, for the bibliographical apparatus of the historical sciences
is being renewed, at the present time, with astonishing rapidity. A book
on the repertories for the use of scholars and historians is, as a
general rule, out of date the day after it has been completed.

III. The knowledge of repertories is useful to all; the preliminary
search for documents is laborious to all; but not in the same degree.
Certain parts of history, which have been long cultivated, now enjoy
the advantage of having all their documents described, collected, and
classified in large publications devoted to the purpose, so that, in
dealing with these subjects, the historian can do all that need be done
at his desk. The study of local history does not generally require more
than local search. Some important monographs are based on a small number
of documents, all belonging to the same collection, and of such a nature
that it would be superfluous to look for others elsewhere. On the other
hand, a humble piece of work, such as a modest edition of a text of
which the ancient copies are not rare, and are to be found scattered in
several libraries of Europe, may have involved inquiries, negotiations,
and journeys without end. Since the majority of the documents of
mediaeval and modern history are still unedited, or badly edited, it may
be laid down as a general principle that, in order to write a really new
chapter of mediaeval or modern history, it is necessary to have long
haunted the great depositories of original documents, and to have, if we
may use the expression, worried their catalogues.

It is thus incumbent on every one to choose the subject of his labours
with the greatest care, instead of leaving it to be determined by pure
chance. There are some subjects which, in the present state of the
instruments of research, cannot be treated except at the cost of
enormous searches in which life and intellect are consumed without
profit. These subjects are not necessarily more interesting than others,
and some day, perhaps to-morrow, improvements in the aids to research
will make them easily manageable. It is necessary for the student
consciously and deliberately to make his choice between different
historical subjects depend on the existence or non-existence of
particular catalogues of documents a