688 



POPULAR SCIENCE MONTHLY. 



If the two vases which are represented in the view by vertical 

 and horizontal, straight and curved lines, were actually before us 

 you would have difficulty in finding any vertical lines, and the hori- 

 zontal lines would turn out to be circles. The lines in the view 

 mark the apparent terminations of the surfaces. For purposes of 

 study, however, you must regard objects of three dimensions as 

 bounded by lines, just as they appear in photographs, drawings, or 

 other flat representations, geometric or perspective. In regarding 

 objects from the point of view of decoration there is still another 

 element to be considered; that is, the element of material, the sub- 

 stance of which objects consist, for it is evident that the ornament 



which would be appropriate to 

 wood, for instance, might not 

 be appropriate to metal or to 

 stone. The element of mate- 

 rial is of great importance in 

 practical decoration, but of less 

 importance in theoretical deco- 

 ration. Lines and surfaces are 

 therefore the two chief ele- 

 ments of decoration to be con- 

 sidered at present. Color, be- 

 ing an element of an entirely 

 independent nature, will not 

 be considered at all. 



First, lines. The lines 

 down one side of an object 

 may be called the profile of 

 the object, while the lines sur- 

 rounding the object may be 

 called the contour or outline 

 of the object. 



Profiles and outlines are made up of any number of straight 

 and curved lines connected at any and every variety of angle. 

 The view (Fig. 2) shows a few possibilities of combination of lines 

 into profiles. The particular thing to be observed in these pro- 

 files is that individual curves are preceded or followed by curves 

 which curve in the same direction or in the opposite direction — 

 that is, regarding the curves as concave or convex from a given 

 side of the profile, sometimes a concave curve meets a concave 

 curve, sometimes it meets a convex curve. In these particular pro- 

 files the straight lines which unite the curves are so small and so 

 insignificant that they appear as mere connections. Where the 

 adjoining curves are homogeneous the connection is called con- 



FiG. 4. 



