We must hold, then, that the alphabetical index of subjects should be the auxiliary and complement of the Alphabetical Catalogue, not a part of it; that each book should be entered in it, as in the catalogue, once and once only; that the minor indexes should be grouped together so as to form collectively a whole (_e.g._ ornithology and ichthyology, as sub-sections of zoology); and that the operations of cataloguing and indexing should go on _pari passu_. If this is attended to for the future, the future will take care of itself; but "not Heaven itself upon the past has power," and it is discouraging to think upon the immense leeway which remains to be made up in most of our great public libraries. The experience of the Bodleian will be very valuable, and we must confess to much curiosity to see how long the operation of classifying its multifarious contents will take. In the British Museum the foundation of a classed catalogue has already been laid by a simple process. As fast as the titles have been transcribed for insertion in the three copies of the catalogue by a manifold writer, a fourth copy has been taken, and this copy is arranged in the order of the books on the shelves. As the various subjects are kept together in the library, such an arrangement is practically equivalent to a rough classed catalogue, which could be digested into order with comparative facility. The publication of such a classified index, reduced to the utmost possible brevity, offers, as it seems to us, the best solution of the vexed question of the publication of the Museum Catalogue. On this point much remains to be said. Meanwhile, before quitting the subject of cataloguing methods, a tribute is due to Mr. Cutter's important contribution to the subject, in his rules for his Dictionary Catalogue. Next after the settlement of the Museum rules in 1839, these form the most important epoch in the history of cataloguing. Agreeing with the latter rules in the main, and when differing, generally, as we must think, not differing for the better, they nevertheless contain a most valuable body of acute reasoning and apt illustration, which it did not fall within the province of the Museum authorities to provide; they bring unusual experience and ability to bear upon the intricate subject of classification, and are further reinforced by most ingenious remarks on the economy and manipulation of print, making the mere variations of type instructive.