Sadly, on-line catalogues are terrible at subject searches; their noise level, in the informational sense, is incredible. Card catalogues have the sense not to shuffle together alphabetically the myriad subheadings for “labor” in the medical sense and “labor” in the A.F.L.-C.I.O. sense; the on-line catalogues I’ve seen don’t. Card catalogues don’t lump subheadings for, traffic control in Alexandria, Virginia, together with ones for the lost library at Alexandria, Egypt, either. The “See also” card at the beginning of a set of subject entries in a card catalogue didn’t yank you to another part of the catalogue, and abandon you there; it just suggested that you might want to expand your search in various directions if you didn’t find enough where you stood. There is no real equivalent for this yet in on-line catalogues, nor is there an equivalent for guide cards—those that stick up above the rest, with typed headings—which constitute a sort of loose outline of knowledge built into the trays, and help you to keep your bearings. Card catalogues are “precoÖrdinated,” whereas on-line catalogues are still almost entirely “postcoÖrdinated,” which means that the burden of figuring out how the universe of subjects ought to be organized has been shifted away from the cards and onto you, the user, who must now master Boolean “AND NOT” operators and keyword trickery and crabwise movement by adjacent call numbers merely in order to block avalanches of irrelevancies.