FRANCK THOMAS ARNOLD (1861--940) was educated at Rugby and Trinity College, Cambridge. In x886 he was appointed lecturer in German Language and Literature at the University College of South Wales and Monmouth, a post he held for forty years. All his life he took a deep interest in music and was an enthusiastic amateur of the violoncello. The world has every reason to be grateful that Arnold's official duties at Cardiff left him with sufficient leisure to indulge his hobby which led him to explore minutely the subject of writing and playing from a thorough-bass. Besides contributing from time to time to many musical journals-' Bach-Jahrbuch ', 'Proceedings of the Musical Association', ' Musical Times', 'Music & Letters', 'Zeitschrift fur Musikwissenschaft ' -he suppljed the article on Thorough-bass for Grove's'Dictionary of Music and Musicians'. Years of research culminated in his writing a monumental treatise on thorough-bass which is recognized to-day as the standard authority. Ernest Newman, in 'The Sunday Times' of July 2nd I944, paid a glowing and well-deserved tribute to Arnold when he described his' Art of Accompaniment from aThoroughBass '1 as the greatest work of musicography ever produced in this country. This great book is a lasting monument of patient and exhaustive scholarship. Arnold in his search for a full knowledge of his subject was not content with drawing upon the resources of the libraries of Europe, but he also bought for himself all available literature and music from which he could absorb and note at leisure anything relating to thorough-bass. As a result of these activities, spread over a number of years, he gradually built up an important and valuable collection of music and literature of music. The theoretical works, especially those on harmony and thorough-bass, range from Zarlino's 'Le istitutioni harmoniche', I562, to Albrechtsberger's ' Kurzgefasste Methode den Generalbass zu erlernen ', 2nd ed., 1837, and include most of the recognized authorities. His other acquisitions form a remarkable collection of eighteenth-century instrumental music. Both sections contain works of great importance and rarity, indeed some editions and issues are unique. It is not intended here to describe the collection fully for, in addition to a printed list appearing in the 'Cambridge University Reporter' for February 6th 1945, a manuscript catalogue has been made containing the titles of the works, together with some notes pointing out the essential differences in some of the editions and issues, and answering (and no doubt raising) some curious bibliographical questions. Perhaps one should single out Praetorius, ' Syntagma musicum' as one of the show pieces . Complete copies of this work are very rare, and this copy is complete except for the title-page to Volume I. The curious puzzle date (I614) is given twice on the general title-page. Mersenne, ' Harmonie universelle ', is here to exasperate the bibliographer with its erratic and faulty pagination and its ever-changing order of the various sections. I have yet to see two copies bound in the same order, and indeed it must be one of the most tiresome of books to collate. What is said to be the best collation is to be found in the ' Hirsch Music Library Catalogue ', Vol. I.