THE annotated catalogues of antiquarian booksellers who deal especially in old scientific books always make interesting and instructive reading to the student of the history of science. Sometimes these catalogues form the medium for the first announcement of bibliographical discoveries of importance. A case in point is afforded by a catalogue (No. 73) recently issued by Messrs. Davis and Orioli, of 37 Museum Street, London, W.C.I. In this list, there is offered for sale a book that the vendors claim to be the hitherto undescribed first printed text of Petrus Peregrinus's treatise “De Magnete”. The book in question, a small quarto of six leaves, is entitled “De Virtute Magnetis”, and its title page bears the name of Raymundus Lullus as author; but no date or place of printing is indicated. The text is almost identical with that of the edition of Peregrinus's treatise published at Augsburg in 1558, hitherto regarded by bibliographers as the first printed edition. The original “Epistola De Magnete” was written in the thirteenth century, probably in 1269, and several early MSS. copies exist. In a long and interesting note, Messrs. Davis and Orioli give reasons for believing the book they describe to have been printed at Rome by E. M. Silber, not later than the year 1520. They state that, in the past, Peregrinus's treatise has been ascribed both to Raymond Lull and to Roger Bacon, and it is suggested that these authors' names may have been used in a general way during the Renaissance as possible authors of any scientific works. While the 1558 edition is a book of extreme rarity, Messrs. Davis and Orioli have so far only been able to trace one other copy of “De Virtute Magnetis”, that in the Bibliotheque Nationale, Paris.