2 72 THE POPULAR SCIENCE MONTHLY 



parts of a single exposition. The crudest defect in illustration is a 

 neglect of this fundamental requirement, yet it is a fault which has wide 

 prevalence in certain forms of book-making to-day. A fixed amount of 

 illustration per chapter, or hundred pages, is supposed to be expected by 

 the reader, and an illustrator is engaged to furnish the required number 

 of pictures. In the class of books where this custom prevails — for ex- 

 ample, in light fiction — the quality of the demand for illustration falls 

 to its lowest point. There is practically no situation the understanding 

 of which requires visual exemplification. The story itself is commonly 

 little more than a succession of pictures, each relatively simple and 

 having a completely obvious relation to its neighbors. It is partly, at 

 least, because the reader's demand is so far from exacting that such 

 slight consideration is given to the really illustrative character of pic- 

 tures in works of this class 



When the primary function of the picture has thus lapsed, the reason 

 for its introduction is to be sought elsewhere ; for value of some kind it 

 must possess if its introduction is not to be regarded as a sheer miscon- 

 ception of the reader's desire. This reason is to be found, it need hardly 

 be said, in the mere decorative function of the picture. It is a trivial 

 motive, which also ignores a fundamental canon of esthetics, yet one 

 which has a distinct psychological value. It neglects the require- 

 ments of esthetics, for if the making of a book be treated as a work 

 of art, everything which appears between its covers should be instru- 

 mental to the development of the central conception for which the 

 work stands. No picture, from this point of view, is admissible which 

 does not help — in the strictest sense, which is not indispensable — to 

 make the meaning clear. But if the principle of function be neglected, 

 a multitude of pictures may be introduced in a merely illustrative, as 

 opposed to explanatory, way. One might, for example, insert the picture 

 of a pen or inkstand each time the article was mentioned, though an 

 acquaintance with these things on the part of the reader is fairly to be 

 assumed. Such illustration of course has its place wherever the objects 

 in question are unfamiliar and the reader is liable to construct in imagi- 

 nation a wrong representation of them. 



Further, if the principle of unity be ignored the illustrations which 

 are introduced may be chosen in virtue of any element of desirability 

 which they possess. Value of this kind has a wholly indefinite range. It 

 may be merely quantitative : so many pictures to so many pages of text ; 

 no bunching of illustrations in one part of the work while another is left 

 bare; and the like. But such rules refer only to the distribution of 

 pictures, not to their introduction itself. If illustration be not invari- 

 ably an elucidation of the text, as it clearly is not, it must satisfy some 

 other human need, or pictures would not then be found in books. One 

 such motive has already been mentioned: the decorative sense. The 

 picture satisfies an elementary esthetic demand. It is introduced as the 



