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cumulation of mere yellow, that to add more would give an idea of 
another colour bordering on orange. The same of red and blue. 
Black is as it were a supersaturation of the darkest tints : thus full 
brown or saturate brunneus with a supersaturate portion of blue will 
be analogous to black. Grays may be made upon this principle by 
adding a portion of blue to the light and middle browns. 
Having reconciled the primitive of all tints, and colours, on the 
most permanent basis, it becomes necessary to speak of the material 
colours, it being one of the first objects of my intention to simplify 
them. 
MATERIAL COLOURS USEFUL TO ARTISTS. 
The most perfect are those that have some transparency, as they 
may be applied with greater variety, and as every object is seen 
through a transparent medium, which helps to give an effect that 
the artist is otherwise too often unable to accomplish, and for 
which much pains is taken by glazing with the help of gum or 
varnish assisted with asphaltum. I should think that, the fewer the in- 
gredients the more perfectly they may be understood ; but, being 
easily comprehended, perhaps they may be more casually passed 
over ; yet it were better to understand a few things well, than to be 
confounded with a multitude. 
It happens that what are called material colours are not all so per- 
manent as might be desirable, and the artists in oil or water colours, 
and even in enamel, are often much troubled to accomplish their ends 
on this account. Mineral colours for enamel are often so tender as 
easily to be affected by a small difference of heat in fixing, and those 
for oil or water colours often readily change by exposure to air. 
Vegetable colours are more used in water or size colourings or paint- 
ings, but are only fit to be kept in portfolios or books. Colours from 
animal substances are least in use; and although Nature allows us ta 
procure colours from either of these three great divisions for our dif- 
ferent uses, they may all depend upon nearly the same bases ; which 
however yet remains to be found out. I will now enumerate the 
