Thus much respecting the Musical Library in the British Museum. Let us now consider how a national musical library ought to be constituted. Premising that it is intended as much for the use of musical people who resort to it for reference, as for those who are engaged in a continued study of some particular branch of the art, the following kinds of works ought to form, it would appear, the basis of its constitution. 1. _The Scores of the Classical Operas, Oratorios, and similar Vocal Compositions, with Orchestral Accompaniments._--Many of these scores have not appeared in print, but are obtainable in carefully revised manuscript copies. 2. _The Scores of Symphonies, Overtures, and similar Orchestral Compositions._--The editions which have been revised by the composers themselves are the most desirable. The same remark applies to the scores of operas, oratorios, etc. 3. _Vocal Music in Score._--The sacred compositions _Alla Cappella_, and the madrigals of the old Flemish, Italian, and other continental schools, as well as those of the celebrated old English composers. The choruses of the Greek Church in Russia, etc. 4. _Quartets, Quintets, and similar Compositions in Score._--The study of these works of our great masters is so essential to the musician, that special care should be taken to secure the best editions. The classical trios for pianoforte, violin, and violoncello, and some other compositions of this kind, originally published in parts, have more recently been issued in score. The latter editions are greatly preferable to those in which the part for each instrument is only printed separately. The same remark applies to the concertos of Mozart, Beethoven, and other masters, which have been published with the orchestral accompaniment in score, as well as with the orchestral accompaniment arranged for the pianoforte or for some other instruments. 5. _Sonatas, Fantasias, Fugues, etc._--Of all the classical works composed for a single instrument, the original editions, generally revised by the composers themselves, are indispensable. Besides these, the most important subsequent editions of the same works would be required. Beethoven's pianoforte sonatas, for instance, have been re-edited by several eminent pianists. It is instructive to examine the readings of these musicians, which differ in many points from each other. 6. _Arrangements._--Those of operas, oratorios, masses, and other elaborate compositions with orchestral accompaniment, must necessarily be confined to the instrumental portion, otherwise they are useless either for study or reference. Those arrangements are greatly preferable which have been made by the composers themselves, or under their superintendence.