As it does not come within the plan of the present volume to give a catalogue of all the subjects contained in the block-books to which it may be necessary to refer as illustrating the progress of wood engraving, I shall confine myself to a general notice of the manner in which the cuts are executed, with occasional observations on the designs, and such remarks as may be likely to explain any peculiarity of appearance, or to enable the reader to form a distinct idea of the subject referred to. At whatever period the Apocalypse, the History of the Virgin, and the Biblia Pauperum may have been executed, the former has the appearance of being the earliest; and in the absence of everything like proof upon the point, and as the style in which it is engraved is certainly more simple than that of the other two, it seems entitled to be first noticed in tracing the progress of the art. Of the Apocalypse,--or “Historia Sancti Johannis Evangelistæ ejusque Visiones Apocalypticæ,” as it is mostly termed by bibliographers, for the book itself has no title,--Heineken mentions no less than six editions, the earliest of which he considers to be that described by him at page 367 of his “Idée Générale d’une Collection complète d’Estampes.” He, however, declares that the marks by which he has assigned to each edition its comparative antiquity are not infallible. It is indeed very evident that the marks which he assumed as characteristic of the relative order of the different editions were merely arbitrary, and could by no means be admitted as of the slightest consequence in enabling any person to form a correct opinion on the subject. He notices two editions as the first and second, and immediately after he mentions a circumstance which might almost entitle the third to take precedence of them both; and that which he saw last he thinks the oldest of all. The designs of the second edition described by him, he says, are by another master than those of the first, although the artist has adhered to the same subjects and the same ideas. The third, according to his observations, differs from the first and second, both in the subjects and the descriptive text. The fourth edition is from the same blocks as the third; the only difference between them being, that the fourth is without the letters in alphabetical order which indicate the succession of the cuts. The fifth differed from the third or fourth only in the text and the directing letters, as the designs were the same; the only variations that could be observed being extremely trifling. After having described five editions of the book, he decides that a sixth, which he saw after the others, ought to be considered the earliest of all.[II-36] In all the copies which he had seen, the impressions had been taken by means of a rubber, in such a manner that each leaf contained only one engraving; the other side, which commonly bore the marks of the rubber, being without a cut.