99 
most perfect colour ; may be used in mixtures with the 
same facility as gamboge, from thin, nearly transparent, 
to strong, nearly opaque. 
2 Vermilion, sometimes approaches this, but generally borders 
on orange or scarlet, that is, having a little yellow mixed. 
So we have but one perfect red. Those called red ochre 
or Venetian red are comparatively yellow or brown reds ; 
the first is useful in oil, the latter in water or size. 
1 Prussian blue may be used in water or oil ; it is the most perfect 
blue we know, but has a purplish tinge in some in- 
stances. It is extremely useful in forming greens with 
gamboge, and purples with reds, and ternaries or browns 
with both. 
2 Indigo blue, chiefly useful for fixing shades that are to be 
worked over in water colours, is dull. 
3 Smaltblue,most permanent, most rich vvitharedcast,difficulttouse. 
The best yellows, reds and blues will form good binaries, as men- 
tioned above. 
The local binaries, if I may so call such as nature produces chemi- 
cally, and as it were without apparent mixture, are : 
1 Vermilion, sulphuret of quicksilver, used in oil or water, is li- 
able to change on exposure to air; oil or varnish defends 
it, which gum Arabic does somewhat as a water colour. 
2 Orpiment, sometimes yellow, liable to change. 
3 Orange or red lead, liable to change. 
4 Chromate of lead, changes green with heat, has not been much 
used in England. 
1 Verdigrise, used in water or oil, very bright yellow or blue, 
may have gamboge mixed with it, changes most in oil. 
2 Terre-verte, used in oil, not bright but durable, probably used 
by the ancients of the Venetian school : see Bril. Min. 
tab. 272. 
The three best primitives will make any ternaries, if well managed, 
and even produce the blackest effect possible. 
