gratefully—partly by a resolute determination not to aim at an ideal perfection, which, under the circumstances, would be absolutely mischievous. Ordinary visitors to the library may from one point of view be divided into two classes, those who are astonished that it has not got every book in the world, and those who marvel that it possesses so many books as it does. Nothing is commoner than the remark, "I suppose you have everything that ever was printed," unless it is the exclamation, "You surely do not keep all the rubbish!" These two sets of ideas may be taken to represent the two tendencies which affect every public library; and by consequence every complete catalogue of its contents, that of mechanical accretion, and that of intelligent selection. The operation of the Copyright Act is, of course, responsible for most of the element of "rubbish" in the catalogue; while a moment's thought will show the impossibility of making the librarian a censor, and allowing him to exclude whatever might not square with his prejudices or fancies. A considerable part of the catalogue, therefore, must be devoted to recording publications of little intrinsic value, but even here there is an important reservation to be made. Time, which in so many instances abates the value of what is really precious, makes in a fashion amends by bestowing worth on what was once of little account. What would we not give for a _Court Gazette_ of the days of Augustus, or a list of odds at the Olympic games? There is absolutely no telling what value the most insignificant details of the nineteenth century may possess for the nineteenth millennium: even now men of letters might find the same intellectual stimulus in many a trivial page of the Museum Catalogue, as a distinguished living orator is said to find in Johnson's Dictionary. Next to this automatic factor in the increase of the catalogue may be named the element of seeming accident—the addition to the library of various classes of books, now at one time, now at another, as apparent chance, but actual law has prescribed. If we can imagine the various constituents of the Museum Library piled upon one another in chronological sequence, and a shaft driven down from the top, we may conceive ourselves coming upon a succession of strata, as the geologist finds when he bores for coal, or the archæologist when he explores the site of a city where men have dwelt from the age of Hercules to the age of Heraclius. The Museum was founded by a great physician; the library, therefore, rests upon a sound substratum of old medical books. The King was the next important benefactor; next above early medicine and natural history, accordingly, comes a stratum of royal libraries from the first Tudor to the last Stuart, each a miniature representative of the best literature of its time. The Hanoverian sovereigns, though no great patrons of letters, were diligent collectors of pamphlets: hence the