A notation must be simple, brief, and flexible. Consider the extent to which the principal schemes meet these requirements, and weigh the advantages and disadvantages of a “pure” notation, as in the Decimal, or a “mixed” notation, as in the Subject scheme. The most notable expansion of the Decimal notation is the “Brussels,” which should be carefully surveyed. Note the mnemonic features of the various notations, as these assist in the rapid interpretation of the symbols, and enable one’s mind to more readily grasp the linking-up of the whole scheme. Notation is of itself insufficient for practical arrangement on the shelves, as the necessity arises for some method of regulating the order of the books within each Division, Section, etc., hence the use of Author Marks. Several tables have been compiled, but the most detailed and best known is Cutter’s, although the other tables must receive due attention as the Cutter Author Marks are not in exclusive use. The arrangement of the books on the shelves is most important, and it is essential to reach the best solutions of the problems regarding “broken sequence,” “oversize books,” etc. It must be remembered that the Library is intended for the use of people who do not want to study the intricate details of a notation in order to find what they want, and it should be made possible for readers not merely to find the subjects they require, but also to find their way about the various classes intelligently, but unaided. To achieve this a most carefully devised method of guiding will be necessary, and all methods and contrivances should be studied, as faulty or insufficient guiding will minimise the benefits of exact classification. READING LIST. Brown--Library classification. _Chap. 5._ Brown--Manual of library economy. _3rd edition._ _Chap. 17._ Coutts--Classification and shelf-guiding. _In Brown and others. Open Access Libraries. Grafton, 1915._ Hopwood--Dewey expanded. _L.A.R. Vol. 9, 1907, pp. 307-322; 340-345_ (_also L.J. Vol. 32, 1907_). Jast--A new book number. _L.W. Vol. 3, 1900-01, pp. 120-123; 150-152._ Purnell--Development of notation in classification. _L.A. Vol. 8, 1911, pp. 25-33; 44-50._ (_Also published separately in L.A.A. Series, but now o.p._) Savage--Classification guides and indexes. _L.W. Vol. 8, 1905-6, pp. 261-266._ Sayers--Canons. _Chap. 7._ Sayers--Elements of notation. _L.W. Vol. 15, 1912-13, pp. 226-231._ Sayers--Grammar. _Principles 21-23._ Sayers--Introduction. _Chaps. 6 and 13._ Stephen--Application of exact classification to shelf arrangement. _L.W. Vol. 11, 1909, pp. 251-255; 325-331._ Stewart--Guiding an open-access lending library. _L.W. Vol. 7, 1904-05, pp. 113-118._ Stewart--Oversize books. _L.W. Vol. 9, 1906-07, pp. 208-211._ QUESTIONS. _1._ What are the essentials of a good notation?