§55 VIII. IX. GROUNDS AND SINGLE COLOURS. 105 



give it a particular tone. Thus when a warmer, or a colder, 

 tone is to be produced, more red, or more blue, may be intro- 

 duced ; but for this and the subject of quantity and 'propor- 

 tion I must refer to Sect. XVIII. The proper hue of each 

 is also a point of great importance ; for when a bright red, 

 blue, or green, is required to agree with another bright colour, 

 the introduction of any one of these of a duller hue than its 

 companion would be fatal to their general effect. This is 

 sometimes the case in the old mosaic pavements at Eome and 

 elsewhere ; but it may be accounted for by the workmen 

 making the best of the materials they had at hand, and being 

 forced to place dull reds and greens in juxtaposition with 

 brighter hues. And it is probable that the heavy red of por- 

 phyry would not have been combined with serpentine if the 

 unlimited choice of brighter and more accordant colours had 

 enabled them to make a better selection.* But it may also 

 be attributed to a vitiated Eoman taste. (See below, p. 151.) 



Of the proper quantity and proportion of colours I shall 

 also treat in Sects. XVIII. and XIX. 



IX. Grounds and Single Colours. — A colour, when used 

 as a ground, has a very different effect, and is under very 

 different conditions from the same introduced in combina- 

 tion with others in a pattern. Thus green, so intractable in 

 large quantities when with other colours, is allowable for 

 covering the walls of a room ; and light green, greyish -green, 

 tea-green, and others, when in large masses, look better if 

 used alone. There is, however, a certain hue of light blue, or 

 bird's-egg-green f, which may even be used as a ground for 

 many other combined colours ; and tea-green is very suitable 

 for a wall hung with pictures, provided it is plain, without 

 any pattern. {See above, p. 97, Sect. IV.) 



* An instance of this may be seen in No. 2 of Mr. Digby Wyatt's interesting 

 collection of the "Mosaics of the Middle Ages," and particularly in fig. 2 ; and 

 again in No. 3, where the want of harmony in the mosaic is remarkable. 



t Bird's-egg-green is rather a hue of green-blue than of green. 



