has been used. Historians endowed with excellent memories, and lazy to boot, have indulged this whim, with the result that their quotations and references are mostly inexact. The human memory is a delicate piece of registering apparatus, but it is so little an instrument of precision that such presumption is inexcusable.
Every one admits nowadays that it is advisable to collect materials on separate cards or slips of paper. The notes from each document are entered upon a loose leaf furnished with the precisest possible indications of origin. The advantages of this artifice are obvious: the detachability of the slips enables us to group them at will in a host of different combinations; if necessary, to change their places: it is easy to bring texts of the same kind together, and to incorporate additions, as they are acquired, in the interior of the groups to which they belong. As for documents which are interesting from several points of view, and which ought to appear in several groups, it is sufficient to enter them several times over on different slips; or they may be represented, as often as may be required, on reference-slips. Moreover, the method of slips is the only one mechanically possible for the purpose of forming, classifying, and utilising a collection of documents of any great extent. Statisticians, financiers, and men of letters who observe, have now discovered this as well as scholars.
The method of slips is not without its drawbacks. Each slip ought to be furnished with precise references to the source from which its contents have been derived; consequently, if a document has been analysed upon fifty different slips, the same references must be repeated fifty times. Hence a slight increase