A large proportion of early printed books are without any indication whatever of their place of origin, printer, or date. The dates are obscured by the quickness or slowness of individual printers in adopting various improvements--sheet-numbering, leaf-numbering, printed capitals, titlepages, methods of imposition, etc.--which thus become uncertain and delusive landmarks. The place of origin is obscured by the existence of almost identical types in different cities and even in different countries. A fortiori the identity of the individual printer may baffle research from types being transferred or copied in all but one or two letters of the fount, which thus become the sole means of differentiating them. As helps the bibliographer has, in the first place, such a classification of the two or three thousand fifteenth century types as he is able to carry in his head. This, in proportion to its completeness, enables him to narrow down the field to be investigated. Some small typographical peculiarity, the way in which the illuminator or rubricator has filled the blank spaces, the note which by good fortune he may have appended in this or some other known copy saying when he finished his work, similar notes by early purchasers which occasionally give the date of their bargain, these and other points may all help forward the happy moment of final identification. Such a hunt as this may sound alarmingly difficult, as if it were all over five-barred gates and inconveniently hedged ditches. But facsimiles and other aids have been greatly multiplied of late years; many a book can be run down and the identification verified in a few minutes, and the possibility of hunting successfully in one's own library presupposes the purchase of many books giving full information as to their origin. These, while offering the means of identifying other books, will themselves raise no questions, so that the collector's life need not be unceasingly strenuous.