from the manuscript substance and that from the writing, then the eye sees no writing, nor does the panchromatic film register it. If, however, the composition of the light falling on the manuscript is controlled and varied by the use of light filters or the employment of artificial light having a different colour structure from ordinary daylight, then the writing may reflect a different composition of colours from that of the material on which it is written, and so will stand out from its background. This phenomenon is especially noticeable when the illumination takes the form of ultra-violet light (provided all other light is excluded). The background emits radiation or fluoresces," while the writing remains black, and so can be easily read. The same thing happens even though the surface ink of the writing has faded, and is illegible in ordinary light. By the use of suitable photographic apparatus, the writing that is visible under ultra-violet light can be permanently recorded. The National Library possesses two fluorescence' cabinets, one of them being the gift of the late Sir J. Herbert Lewis. Their value in deciphering the all but invisible writing on some of our ancient documents is demonstrated by the illustrations facing page 45. These show a part of a manuscript (Peniarth 20) photographed (a) in ordinary light and (b) under ultra-violet light. H. N. JERMAN. THE BROGYNTYN LIBRARY. Last summer the Right Hon. Lord Harlech placed on deposit the literary and historical manuscripts and documents preserved at Brogyntyn, his father having deposited most of the family's purely Welsh manuscripts in 1934. As it is impossible to do justice to such an important and varied collection as this in the compass of a short account, reference may be made to the fuller accounts which were printed in the Library's Annual Report for the years 1933-34 and 1937-38. Scholars have long known something of the collection from A. J. Horwood's account published in the Historical Manuscripts Com- mission's Second Report, 1871, and they have been allowed generous facilities for examining the chief items for two generations at Brogyntyn. The Welsh portion was the most considerable group of early manu- scripts in that language still in private custody in 1934. The remain- der, now also deposited in the National Library, consists of manuscripts ranging from the thirteenth century to the nineteenth and contain- ing English poetry, plays, a thirteenth century psalter, chronicles,