CHAPTER III 



FIRST PRINCIPLES OF THE USE OF MARKINGS WITH OBLITERATIVE SHADING 



HE need of markings is a natural concomitant of the principle of ob- 



literative shading. When an unmarked solid object in a given lighting 

 has been reduced to a perfectly 'flat' monochrome by counter shading, so 

 that it lacks all visible attributes of solidity, it may be quite undistinguishable, 

 provided that its background is of a similar monochrome flat tint. Such is the 

 case in Fig. 14. The solid model is almost undistinguishable, seeming merged 

 into the flat plane of the cloth-covered board, which in reality is several yards 

 behind it. 



Complete 'obliteration' has taken place; for the model, having no dis- 

 tinctive light-and-shade, color, or surface character, is as it were absorbed 

 into its background, and the space in which it stands seems occupied by empty 

 air. But if we now apply a pattern to the background, as in Fig. 15, the case 

 is changed. Though still unsubstantial-looking, and very inconspicuous, the 

 model is clearly discernible as an interruption of the back ground- pattern. If 

 this pattern is small and regular, as in our figure, the whole of the unmarked 

 object's characteristic outline may be traced against it, and by the process of 

 mental inference already alluded to, the observer will recognize it, in spite of 

 its ghostly flatness, as a solid body between him and the background-plane. 

 But behold the effect of applying a like pattern to the model also, as in Fig. 

 16! It immediately recedes again into the flat plane, and the eye loses it even 

 more surely than before, because its likeness to its background is now positive 

 and graphic, at many points. 



The foregoing figures illustrate the simplest form of the use of markings 

 in cooperation with obliterative shading. The next thing for us to consider 



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