In collecting or studying early printed books, one of the most fatal and common mistakes is the undertaking of too much. The day is past when one man will set himself to compile such works as Hain’s _Repertorium Bibliographicum_, or that very much greater book, Panzer’s _Annales Typographici_; both wonderful achievements, but unfinished and imperfect. No one who has not had practical experience can imagine the amount of information which can be obtained by taking a small subject and working at it carefully; or conversely, the amount of careful study and research that is requisite to work a small subject properly. Take as examples Blades’ _Life of Caxton_ and Edmond’s _Aberdeen Printers_, the two best monographs we possess. They contain a very great deal of most careful work, and sufficient material to enable any one who desires to study those particular subjects to do so thoroughly. In collecting, in the same way, a beginner who wishes his collection to be of real value should not be too catholic in his tastes, but confine his attention to one subject. A collection of fifty miscellaneous fifteenth-century books has not, as a rule, more interest than may be associated with the individual books. But take a collection of fifty books printed in one town, or by one printer. Each book is then a part of a series, and obtains a value on that account over and above its own individual rarity or interest. The arrangement and cataloguing of early printed books is a part of the subject which presents many difficulties, In many great collections, these books, for purposes of bibliographical study, are absolutely lost. They are not bought, at any rate not once in twenty cases, for their literary value, but simply and solely as specimens of early printing or curiosities. But, having been bought, they are treated as any other book bought solely for its literary value, and in no other way, _i.e._ they are catalogued under the author or concealed in mazes of cross-reference. If such books are to be bought at all, they should surely be treated in some way which would enable them to fulfil the object for which they were acquired. In the University Library, Cambridge, the fifteenth-century books are all placed together arranged under countries according to size, with a press-mark indicating the country, the size, and the consecutive number. Thus any new acquisition can be added, and placed at once without disarranging the order on the shelves. Any further subdivision, as, for instance, under towns, is impracticable on the shelves, but must be done on paper.