Other kinds of catalogue co-operation are those in which more than one library has joined in the issue of a catalogue to cover the stock of all in certain subjects. A small example was the _Union Class-List of the Libraries of the Library and Library Assistants’ Association_, 1913; and larger examples are the _Classified Catalogue on Architecture, etc., in the Principal Libraries of Manchester and Salford_, 1909, which was edited by Henry Guppy and Guthrie Vine for the Joint Architectural Committee of Manchester; and the Newcastle _Classical Catalogue_, 1912, which contains certain periodicals and books in the Armstrong College Library, as well as those in the Public Libraries. The most recent examples are series of class-lists on important subjects such as Internal Combustion Engines and Aeronautics, both 1918, issued by the Committee on Joint-Technical Catalogues, Glasgow, which bring together titles from the libraries of eighteen institutions in that city, indicating the location of the various books by abbreviations added to the entries, as: Cassier’s Engineering Monthly. E. Kp. L. Ml. P. Pp. S. St. U. Many schemes for a national central co-operative catalogue have been drawn up, and lie buried in the pages of library periodicals, until some future time when the benefits of such work will be realized and recognized in this country. CHAPTER XIX MECHANICAL METHODS OF DISPLAYING CATALOGUES =268.= We have dealt already with forms of catalogue to some extent, but the five chief methods of displaying manuscript catalogues merit a more detailed consideration and illustration. It is needless to attempt to describe every device which has been introduced for the purpose of displaying catalogues and providing for additions and expansion, and we shall limit our selection to those which are best known, most effective or most used. The five chief methods are the Page, Card, Sheaf, Placard and Panoramic, a nomenclature suggested in an article which appeared in 1893 in the _Library_, pp. 45-66. =269. Page Catalogues.=--The most elementary form of the page catalogue is the ordinary manuscript book, with stepped thumb-index or simple alphabetical division of the leaves, so many being allowed for each letter of the alphabet. This is an unsuitable variety for a public library, and should not be used for cataloguing purposes.