56 The Library. Derepas, of Paris. 13 It was not particularly described as a catalogue holder, however, but rather as an ordinary binder: The last of the " Sheaf" catalogue holders which I propose to mention is that patented by myself last year. This has a flexible expanding and contracting back, and the slips are bound by the action of two cylindrical screws, turned by a metal key. It is not necessary, as in the cases of all other " Sheaf" holders, to undo this one in order to remove the slips to make an addition, the loosening of the screws being all that is necessary. The keyed slot cut at the back of the slips gives a sufficient catch, when the screws are tightened, to firmly bind the slips in place. The book numbers, if written on to the clamped portion of the slips, will remain in the books, if entries should be wilfully torn out, and so no catalogue could be made imperfect without the librarian's knowledge. The little xylonite label-holder on the back enables contents slips to be changed at will, without damaging the back. These holders should be kept in numbered pigeon-holes, which will facilitate finding and replacement. Their small size makes them very convenient for general use, and they occupy very little space compared with their capacity. One of these volumes will hold, on an average, 1,000 entries, and it occupies but 56 cubic inches of space. A card tray, to hold a similar number of entries, will occupy at least 225 cubic inches. The whole of the " Sheaf" systems have advantages not to be got from any other method at the same cost. As both sides of each slip can be used for the works of the same author, and each slip can carry from one to a dozen entries, it follows that a moderately sized volume will hold a comparatively large number of titles. The Staderini holder, on thin paper, contains 450 leaves ; with linen mounts, 320. Sacconi's ordinary holder has a capacity of 250. The Leyden, and similar holders, are strongest when kept thin, and, probably, 150 slips would be a maximum. My own variety of holder will contain 600 thin manilla slips for type-writing, 500 of fairly thick paper for handwriting, and from 300 to 350 thick manilla or ledger paper slips. I allow, as the result of careful calculation, an average of two entries per slip in an author catalogue, where one writer's works can be recorded on a single slip. For the convenience of those who desire a comparison of storage capacities and prices, I have compiled a table, which shows at a glance these particulars for " Card " and " Sheaf" catalogues : 13 Patent Specification, No. 13,229, iSSi.
