_4._ Author Bibliographies--Books or articles by, or by and about, a particular author, _e.g._, “Bibliography of the works of Shakespeare,” by W. Jaggard. _5._ Subject Bibliographies--Books and articles about a special subject, _e.g._, Woodbury’s “Bibliography of Cotton Manufacture.” _6._ Bio-Bibliographies--a compilation giving the biographies of writers and lists of their writings, _e.g._, Allibone’s “Dictionary of Authors.” (_3_) WHY PREFATORY PAGES ARE SOMETIMES NUMBERED IN ROMAN FIGURES. Prefatory pages are numbered in Roman figures because they are usually printed after the body of the book has been “set up.” In many cases the printer has no estimate of prefatory matter and to overcome the difficulty he numbers the text in Arabic and the preliminary pages in Roman figures. (_4_) “NATURAL HISTORY” BIBLIOGRAPHY. Panzer has been spoken of as “the one true naturalist among general bibliographers,” and since his day two distinct methods of bibliography have grown up. One method treats specimens of early printing simply as curiosities, and their value only depending according to their rarity or intrinsic worth, or again to some peculiar characteristic found in them. This method is generally associated with the name of Dibden. The other method, which is called by Henry Bradshaw the “natural history method of bibliography” is associated with the name of Panzer, who was the first practical exponent. By this method each press must be looked upon as a _genus_, and each book as a _species_, and the more or less close connection of the different members of the family must be traced by the characters which they present to our observation. Bradshaw’s own work is the best example of this method, and the beginner can follow no better model than the papers he wrote on early printing. (_5_) TYPOGRAPHY. “POINT SYSTEM.” A unit of measurement has been accepted as a standard for the purpose of enabling the products of different manufacturers to be used together. The unit of measurement adopted in this country and America is the Pica which is approximately one-sixth of an inch in width. TYPE BODY SIZES.