A work on illustrated books, if it is itself to be illustrated, suffers one serious disadvantage. The original graphic processes - etching, wood-engraving, lithography and the rest - must inevitably lose some of their individual quality owing to the effect of photographic reproduction. Thus, a woodcut has to be reproduced by means of a line-block, an etching by photogravure, or an aquatint by photo-lithography. Again, illustrations of widely varying sizes must be made to conform with the format of the book in which they are reproduced. In this instance, therefore, it has been thought preferable to choose illustrations which require the minimum of reduction rather than to reproduce in little within the modest dimensions of this book some of the pages from larger books which readers would doubtless expect to find reproduced ... - from the Introduction