The whole of the devices just described are so arranged that leaves can be inserted, to a more or less limited extent, at any point. The British Museum type does not provide for unlimited additions, nor for any subsequent division of volumes, without much trouble and rebinding. The French and other adjustable leaved binders do allow for unlimited insertions, subject to the condition that the matter mounted on the pages must be redistributed. In an adjustable book new leaves can be inserted at any place till the volume is full, and then the contents may be divided and two books used, this subdivision and spreading being continued as the entries increase in number. =272.= A form of page catalogue combining the powers of inserting new leaves at any point, and moving single entries about without having to paste them down or lift them up, is called the Rudolph Indexer. It consists in its book form of thick cardboard leaves, to which metal flanges are secured, down each margin. Each leaf is provided with a double-hinged fastening, which enables it to be hooked on to any adjoining leaf, so as to form a volume of any desired thickness, to which a pair of covers can be attached. The catalogue entries are written or printed on narrow cards, and these are slipped under the flanges, which secure them by either end. Fig. 94 shows at a glance the appearance of this form of page catalogue. [Illustration: FIG. 94.--Rudolph Indexer Book (Section 272).] =273.= There are certain advantages claimed for page catalogues which may be enumerated here. The chief is that a large group of entries can be scanned with one sweep of the eye, thereby facilitating the rapid finding of any particular entry. Another is that, being in book form, it is more easily manipulated than other forms of catalogue. Its comparative cheapness is sometimes put forward as an advantage over other forms, particularly cards, but on this point it is not wise to assume cheapness where so much time and labour are necessarily involved. As regards the claim to rapidity in turning up entries because a whole page is exposed at a time, there are considerable doubts as to its soundness. General experience of such catalogues as the British Museum is that, owing to the number of entries, the occasional congestions and disorders where double columns of entries exist, it is more difficult to find a given entry than in the case of cards or slips properly guided and in accurate alphabetical order. This point may be further illustrated by the case of men or women who are not adepts at using alphabetical lists, and who turn up a particular word in a dictionary with much difficulty and loss of time. [Illustration: FIG. 95.--Card Catalogue Cabinet with Sliding Extension Runners (Section 275).]