The first edition of Professor _Bolton's Catalogue of Scientific and Technical Periodicals_[44] was issued in 1885, and was intended to embrace the principal independent periodicals of every branch of pure and applied science, published in all countries from the rise of this literature to the present time, with full titles, names of editors, sequence of series, and other bibliographical details, arranged on a simple plan convenient for reference; omitting, with a few exceptions, serials constituting transactions of learned societies. In cases where the scientific character of the journal or its right to be classed as a periodical was doubtful, and in other debatable cases, the compiler followed Zuchold's maxim, that "in a bibliography it is much better that a book should be found which is not sought, than that one should be sought for and not found." The new edition contains as Part I a reprint from the plates of the first edition, with such changes necessary to bring the titles down to date as could be made without overrunning the plates; and in Part II additions to the titles of Part I that could not be inserted in the plates, together with about 3,600 new titles, bringing the whole number of titles up to 8,477, together with addenda, raising this number to 8,603, minus the numbers 4,955 to 5,000, which are skipped between the first and second parts. Chronological tables give the dates of the publication of each volume of the periodicals entered. A library check list shows in what American libraries the periodicals may be found. Cross-references are freely introduced. The material for the work has been gathered from all available bibliographies, and by personal examination of the shelves and catalogues of many libraries in the United States and Europe, and from responses to circulars sent out by the Smithsonian Institution. The whole work is a monument of prodigious labor industriously and faithfully performed.