The plan was adopted in the Amherst College Library in 1873, and the work of transferring the entire library to the new catalogue at once commenced.  It was found entirely practicable to make the change gradually, as means allowed, without interfering in any appreciable degree with the circulation of the books.  The three years trial to which it has been there subjected has more than justified the claims of its friends, and it is now printed with the more confidence on this account.  It has been kept in manuscript up to this time, in order that the many minor details might be subjected to actual trial and modified where improvement was possible.  The labor involved in preparing the Classification and Index has been wholly beyond the appreciation of any who have never attempted a similar task.  Much valuable aid has been rendered by specialists in many departments, and nearly every member of the Faculty has given advice from time to time.  Among the many to whom thanks are due, special mention should be made of Mr. C.A.  Cutter, the librarian of the Boston Athenaeum, and Mr. John Fiske, of the Harvard University library, for valuable suggestions and appreciative criticism.  While these friends are in no way responsible for any remaining imperfections in the scheme, they should have credit for many improvements which have been made during these three years of revision.  The essential character of the plan has remained unchanged from the first.  Doubtless other improvements are still possible, and it is hoped that users of the scheme will call attention to any proposed change in the naming or arrangement of the headings, or to any omission which should be supplied in the Subject Index.

Before printing, the plan was submitted to quite a number of librarians for criticism.  Among the hundreds of points raised as to its practical workings and usefulness there was only one in which it was not shown to be equal or superior to any other system known.  This objection applied only to the arrangement on the shelves; not at all to the catalogues or indexes.  It was, that in this relative location, a book which this year stands, e.g., at the end of a certain shelf; may not be on that shelf at all another year, because of the uneven growth of the parts of the library.  This slight objection inheres in any system where the books are arranged by subjects rather than by windows, doors, shelves, and similar non-intellectual distinctions.

In this hurriedly prepared account of his plan, the author has doubtless failed to meet many objections which may be raised and which he could easily answer.  He would therefore ask the privilege of replying personally to any such objections, where they arise, believing that it will be possible to answer, if not all, at least a very large proportion.