My thought about dispensing with shelf-marks in the card and other catalogs (not really my thought, for I had it from one of our leading librarians, who has not, however, put it in practice himself) is that the great difficulties connected with the changing of shelf-marks in catalogs when books are reclassified may be avoided by placing on the card only the accession number (in case of a set the accession number of the first volume), and then maintaining a key, consisting of a book closely ruled in double columns, where for each book in the library the shelf-mark is written in pencil against the accession number and changed whenever the book is renumbered. Such a scheme could not be satisfactorily applied in a library where the looking-up of the shelf-mark is involved in the calling for books in most cases. I am prepared to favor it only where (as is now the case in our own library) a majority of the calls for books are made orally and answered by the attendant without reference to shelf-mark. In our case these calls amount to seven-eighths of all the calls, and in addition to this it should be said that at least one-half the books drawn under our open-shelf system are drawn without any "call" at all, so that we may say, that if we had the "key" system it would come into play for perhaps one-sixteenth of the books drawn. In libraries of moderate circulation like our college and university libraries, and (for all but certain classes which are most used) even in the large public libraries, it seems to me that the key plan may work well. Of course the key if subjected to constant use would be difficult and expensive to maintain, owing to wear and tear. We should not fail to observe that three separate and distinct features of modern library progress are each and all working against the necessity, _i.e._, tending to minimize the necessity, of shelf-marks in the catalog. These are, first, the open-shelf system; second, minute classification and alphabetical arrangement in classes, and third, book-card charging systems. Without enlarging upon these points, I would like to suggest them to you as worthy of consideration.