Care has, of course, to be exercised in "placing" these unfinished books to have space enough for their expansion. If this exceeds expectation, the set of volumes has to be transferred to another shelf, unless the shelf below happens to be empty or, at any rate, only partially filled, and that with books without a third-mark. To allow a "work in progress" to overflow into the shelf next below, if that contains third-marked books, is obviously impracticable without renumbering the whole shelf. The most troublesome of "works in progress" are the "series," which multiply inordinately, according to present fashions of publishing, and give as much trouble as periodicals in forecasting their future development. It is probably best in libraries arranged on the fixed-location system to keep together all works in progress, whether "periodicals" or not, and to mark them on the system of movable press-marks. Even where the latter system prevails throughout, it will save much shifting to keep the works in progress apart. At Brussels and Vienna (Imperial Library), for instance, a separate room is reserved for this purpose, and no "set" or work appearing at successive periods obtains a permanent press-mark until it is complete.
The scheme of classification of the British Museum library is here appended.
