One of the first lessons I learned when applying myself to the study of old books was never, on any account or under any circumstances, to have anything to do with imperfect copies, and I have not so far had any occasion to regret my decision. It is perfectly true that no perfect copies are known of some works, such, for example, as the first or 1562-3 English edition of Fox's _Book of Martyrs_; but books of this class will either never be met with during a lifetime, or will form, if met with, an obvious exception to the rule. Fragments of genuine Caxtons, again, sometimes sell by auction for two or three pounds a single leaf, and even a very imperfect copy of any of his productions would be considered a good exchange for a large cheque; but these are exceptions and nothing more--exceptions, moreover, of such rare practical occurrence as to be hardly worth noting. In the vast majority of instances, when a book is mutilated it is ruined; even the loss of a single plate out of many will often detract fifty per cent. or more from the normal value, while if the book is "cut down" the position is worse. This lesson as a rule is only learned by experience, and many young collectors resolutely shut their eyes to the most apparent of truisms, until such time as the consequences are brought fairly home to them. It is exceedingly dangerous to purchase imperfect or mutilated books, or to traffic in them at all. This position will be enlarged upon during the progress of the present chapter. To return to the reasons which contribute to the value of a book, it may be mentioned that "suppression" is one of the chief. This is a natural reason; others are merely artificial, which may be in full force to-day but non-existent to-morrow, depending as they do upon mere caprice and the vagaries of fashion: with these I have, in this volume at any rate, nothing to do. De Foe, in his _Essay on Projects_, observes: "I have heard a bookseller in King James's time say that if he would have a book sell, he would have it burned by the hands of the common hangman," by which he presupposed the existence of some little secret horde which should escape the general destruction, and which would consequently rise to ten times its value directly the persecution was diverted into other channels. This is so, for where an edition has been suppressed, and most of the copies destroyed, the remainder acquire an importance which the whole issue would never have enjoyed had it been left severely alone. The Inquisition has been the direct cause of elevating hundreds of books to a position far above their merit, and the same may be said of Henry VIII., who sent Catholic as well as Protestant books wholesale to the flames; of Mary, who condemned the latter; of Edward VI., who acquiesced in the destruction of the former; and of Elizabeth and the two succeeding sovereigns, who delighted in a holocaust of political pamphlets and libels.