While discussion respecting the printing of the Museum Catalogue was proceeding, the character of the catalogue itself was undergoing modification. Great additions were daily being made to the number of books. The new entries thus rendered requisite were at first made in the old manuscript catalogue of additions interleaved with the original printed catalogue of Sir Henry Ellis and Mr. Baber. Two alphabetical series of titles, one printed and the other manuscript, were thus comprised within the same volumes. The amalgamation of these two sets of titles, and the consequent absorption of the catalogue commenced in 1839 into a more extensive general catalogue, was effected by the ingenious and admirable suggestion, made independently in 1849 by Mr. Wilson Croker and Mr. Roy, of the Library, that the entries, instead of being written upon the leaf itself, should be written upon movable slips pasted upon it, so that insertions might be made without any disturbance of alphabetical order. The suggestion was promptly adopted, transcribers were engaged to copy the great mass of accumulated titles, and, all thoughts of printing the catalogue commenced in 1839 being laid aside for the present, the titles prepared for it were also transcribed and incorporated with those written for the books newly acquired. In 1851 this new catalogue, transcribed fourfold by the "carbonic" process, and with copious space provided for insertions and interleavings, was placed in the Reading Room in 150 volumes, or about as many as are now occupied by letter B alone. The catalogue of 1839 and the supplementary catalogue were thus put into a fair way to become one, and it became obvious that printing must be deferred until the amalgamation was complete. It was still, however, a fair question whether the catalogue might not be kept up in print; whether it was better to transcribe titles fourfold as we did then, or to multiply them indefinitely by print as we do now. I cannot find that the practicability of keeping up a continually augmenting catalogue in print was seriously considered, until, in October 1861, it was proved by the introduction of print into the University Library of Cambridge. Some years afterwards the system was strongly pressed upon the attention of the Museum by the Treasury, which had remarked the gradual and inevitable increase of expenditure in binding, breaking up, interleaving and relaying the volumes of the manuscript catalogue, increased by this time from 150 to 1500. I well remember the pains which Mr. Rye, then keeper of the printed books, took in investigating the subject, and I believe I may say that had it depended upon him, the transition to print would have been effected immediately. Other views, however, prevailed for the time; and when, in October 1875, the subject was again brought forward by the Treasury, it fell to my lot to treat it from a new point of view, suggested by my