The first thing to seize in an object, in order to draw it, is the
contrast of the principal lines. Before putting chalk to paper, get this
well into the mind. In Girodet's work, for example, one sometimes sees
this admirably shown, because through intense preoccupation with his
model he has caught, willy-nilly, something of its natural grace; but it
has been done as if by accident. He applied the principle without
recognising it as such. X---- seems to me the only man who has
understood it and carried it out. That is the whole secret of his
drawing. The most difficult thing is to apply it, like him, to the whole
body. Ingres has done it in details like hands, &c. Without mechanical
aids to help the eye, it would be impossible to arrive at the principle;
aids such as prolonging a line, &c., drawing often on a pane of glass.
All the other painters, not excepting Michael Angelo and Raphael, draw
by instinct, by inspiration, and found beauty by being struck with it in
nature; but they did not know X----'s secret, accuracy of eye. It is
not at the moment of carrying out a design that one ought to tie oneself
down to working with measuring-rules, perpendiculars, &c.; this accuracy
of eye must be an acquired habit, which in the presence of nature will
spontaneously assist the imperious need of rendering her aspect. Wilkie,
again, has the secret. In portraiture it is indispensable. When, for
example, one has made out the _ensemble_ of a design, and when one knows
the lines by heart, so to speak, one should be able to reproduce them
geometrically, in a fashion, on the picture. Above all with women's
portraits; the first thing to seize is to seize the grace of the
_ensemble_. If you begin with the details, you will be always heavy. For
instance: if you have to draw a thoroughbred horse, if you let yourself
go into details, your outline will never be salient enough.

_Delacroix._