[39]Probably the oldest slide rule now in existence is owned by St. John’s College, Oxford, and is in the form of a brass disc, 1 ft. 6 in. in diameter. It was exhibited along with other instruments in May, 1919. According to the Catalogue of a Loan Exhibition of Early Scientific Instruments in Oxford, opened May 16, 1919, the instrument is inscribed with the name of the maker (“Elias Allen fecit”) and with the name of the donor, Georgius Barkham. It is dated 1635, which is only three years after the first publication of Oughtred’s description of his circular slide rule. It is stated in the Catalogue: “Unfortunately all the movable parts but the base-plate and a couple of thumb-screws are missing. The face of the instrument is engraved with Oughtred’s Horizontal Instrument. The back is engraved with eleven Circles of Proportion as described in Arthur Haughton’s book, a copy of which was presented to St. John’s College by George Barkham, to explain the use of the instrument.” As Arthur Haughton’s Oxford edition of Oughtred’s Circles of Proportion did not appear until 1660, it would seem that the instrument was probably not presented to the College before 1660. As far as is known, the next oldest slide rule is of the year 1654, kept in the South Kensington Museum, London, and is described in Nature of March 5, 1914. It is a rectilinear rule, “of boxwood, well made, and bound together with brass at the two ends. It is of the square type, a little more than 2 ft. in length, and bears the logarithmic lines first described by Edmund Gunter. Of these, the num, sin and tan lines are arranged in pairs, identical and contiguous, one line in each pair being on the fixed part, and the other on the slide.” The instrument is inscribed, “Made by Robert Bissaker for T. W., 1654.” Nowhere else have we seen reference to Robert Bissaker. His slide rule seems to antedate the “Whites rule” mentioned above. [This foot-note was added on October 15, 1919.] UNIVERSITY OF CALIFORNIA PUBLICATIONS Note.—The University of California Publications are offered in exchange for the publication of learned societies and institutions, universities and libraries. Complete lists of all the publications of the University will be sent upon request. For sample copies, lists of publications or other information, address the Manager of the University of California Press, Berkeley, California, U. S. A. All matter sent in exchange should be addressed to The Exchange Department, University Library, Berkeley, California, U. S. A. MATHEMATICS.—Mellen W. Haskell, Editor. Price per volume, $5.00. Cited as Univ. Calif. Publ. Math. Vol. 1. 1. On Numbers which Contain no Factors of the Form p(kp+1), by Henry W. Stager. Pp. 1-26. May, 1912 $0.50