=274. Card Catalogues.=--The card-index is the invention of librarians, and is perhaps the most important contribution to method that commerce owes to them. Cards for library cataloguing purposes were used in France in the middle of the eighteenth century; they were used in Trinity College, Dublin, early in the nineteenth century; and in 1852 they were introduced into the Bank of England for commercial indexing. The plan of keeping cards or slips on edge in boxes or drawers loosely, thereby giving unlimited means of expansion and intercalation, must have occurred to many minds as the best means of maintaining perpetual alphabetical order. Single cards not attached in any way, save temporarily, possess unlimited powers of movability, and can be arranged in any kind of order when assembled in numbers, because each card can be taken away or moved about or fresh cards added at any point in a series, without upsetting any adjoining card, or interrupting alphabetical order. The cards, when arranged in alphabetical order, are separated into small divisions by means of projecting guides, on which are printed subject or author or other words or class numbers, which serve the same purpose as the running catch-words of a dictionary, only they are much more effective, because more conspicuous. They are secured by means of a rod which passes through holes punched in the lower part of the cards, and the rod is either locked or screwed into the back or front of the drawer. =275.= The usual plan is to store the cards in the drawers of a cabinet, marking the contents of each drawer plainly on the outside. Fig. 95 is an illustration of a card cabinet, showing the usual guides and sliding runners to enable the whole extent of a drawer to be pulled free of the cabinet for purposes of examination. [Illustration: FIG. 96.--Cabinet of Card Trays (Section 276).] [Illustration: FIG. 97.--Sideless Card Catalogue Tray (Section 276).] =276.= Another form, which is illustrated above (Fig. 96), shows various improvements, including an adjustable angle-block, for supporting the cards at a suitable angle for easy consultation: this can be screwed up tight at any point in a drawer, so as to hold a smaller or larger number of cards in place; a special form of rod on which the cards are strung or filed, easily removable, but still capable of safeguarding them against misuse or misplacement; a special automatic catch at the front of the drawer to prevent it being pulled out accidentally, but which does not prevent any drawer from being taken away from the cabinet if required. Another important improvement introduced in 1902 was the modification in the sides of trays, whereby the woodwork was cut down so as to lighten the tray and enable the cards to be handled from the sides as well as the top. This variety is known as the “Sideless Tray” (Fig. 97).