[Z59 
in the execution of your art. It is possible, 
that by habits of practice, handed over from 
one to another, or by little inanagements in 
laying colours on the canvass, Where little or 
nothing of the general science has been studied 
and attained, many may _so far succeed as to 
avoid glaring errors, and a violation of those 
iirstxprinciples which have their foundation in 
nature. But that success is at all times 
extremely hazardoue and dependent on chance. 
More frequently it has introduced invincible 
conflicts between the primary and secondary 
colours, 
to 
the 
ruin 
of 
harmony 
and 
aerial 
perspective, and to the overthrow of the artist, 
whenever the picture is glanced upon by the 
eye of scientific discernment. Contemptible 
are the best of such managements, even in the 
hands 
of those tliat 
know them best, 
compared 
with 
full 
the 
of 
and masterly possession 
Phi- 
losophy by which this part of your art must be 
guided. If the ordonnance of coloui", on each 
figure "and on the whole, is hot disposed accord- 
ing to the immutable laws of the science, no fine 
effect, or accordant tones of colours, can possibly 
be produced. There is, therefore, but ohe way-'