I think that the rule of never mixing incongruous subjects within the same cover should be adhered to. The expense, by the cheaper method of binding referred to, is but slightly greater than must be incurred by binding several in a volume, in solid half morocco style. But, whenever pamphlets are bound together, the original printed paper covers should never be destroyed, but should be bound in. Another method of preserving pamphlets is to file them away in selected lots, placed inside of cloth covers, of considerable thickness. These may be had from any book-binder, being the rejected covers in which books sent for re-binding were originally bound. If kept in this way, each volume, or case of pamphlets, should be firmly tied with cord (or better with tape) fastened to the front edge of the cloth cover. Never use rubber or elastic bands for this, or any other purpose where time and security of fastening are involved, because the rubber will surely rot in a few weeks or months, and be useless as a means of holding together any objects whatever. Still another means of assorting and keeping pamphlets is to use Woodruff's file-holders, one of which holds from ten to thirty pamphlets according to their thickness. They should be arranged in classes, placing in each file case only pamphlets on similar subjects, in order of the authors' names, arranged alphabetically. Each pamphlet should be plainly numbered at its head by colored pencil, with the figure of its place in the volume, and the number of the case, containing it, which should also be volumed, and assigned to shelves containing books on related subjects. I need not add that all these numbers should correspond with the catalogue-title of each pamphlet. Then, when any one pamphlet is wanted, send for the case containing it, find it and withdraw it at once by its number, place it in one of the Koch spring-back binders, and give it to the reader precisely like any book that is served at the library counter. A more economical plan still, for libraries which cannot afford the expense of the Woodruff file-holders, is to cut out cases for the pamphlets, of suitable size, from tough Manila board, which need not cost more than about three cents each case. In whatever way the unbound pamphlets are treated, you should always mark them as such on the left-hand margin of each catalogue-card, by the designation "ub." (unbound) in pencil. If you decide later, to bind any of them, this pencil-mark should be erased from the cards, on the return of the pamphlets from the bindery. CHAPTER 8. PERIODICAL LITERATURE.