“ Every one agrees nowadays ”, observethe most noted French writers on the study of history, “ that it is advisable to collectmaterials on separate cards or slips of paper. . . . The advantages of this artifice areobvious; the detachability of the slips enables us to group them at will in a host ofdifferent combinations; if necessary, to change their places; it is easy to bring textsof the same kind together, and to incorporate additions, as they are acquired, in theinterior of the groups to which they belong ” (Introduction to the Study of History,by Charles Langlois and Charles Seignobos, translated by C. G. Berry, 1898, p.103). “