at in _flat biting_ the work
of the acid is accomplished all over the plate at one and the same time,
and with only one immersion in the bath, while in _biting with
stopping-out_ there are several successive, or, if you prefer the term,
partial bitings, between each of which the plate is withdrawn from the
bath, and the parts to be reserved are stopped out with varnish as often
as it is thought necessary.

It follows from this, that, with flat biting, the modelling must be done
by the needle, using either only one needle, or else several of
different thicknesses.

67. =Flat Biting.--One Point.=--With a single needle the values are
obtained by drawing the lines closely together in the foreground and
nearer distances, or for passages requiring strength, and by keeping
them apart in the off distances, and in the lighter passages of the near
distances; furthermore, to obtain a play of light in the same distance,
the lines must be drawn farther apart in the lights, and more closely
together in the shadows. A single point gives a hint of what we desire
to do, but it does not express it. It is undoubtedly sufficient for a
sketch intended to represent a drawing executed with pen and ink or with
the pencil; but it cannot be successfully employed in a plate which, by
the variety of color and the vigor of the biting, is meant to convey the
idea of a painting.

68. =Flat Biting.--Several Points.=--When several points of different
thickness are used, the coarser serve for the foreground and near
distances, the finer in gradual succession for the receding distances.
They are used alternately in the different distances, and the lines are
drawn more closely together here, or kept farther apart there, according
to the necessities of the effect to be obtained; the depth of the biting
is the same throughout, but the difference in thickness of the lines
makes it an easy matter, by more elaborate modelling, to give to the
etching the appearance of a finished design.

With a single point, as well as with several, the pressure used in
drawing must remain the same throughout, so that the acid may act
simultaneously, and with equal intensity on all parts of the plate. If
there has been any inequality of attack, the values will be unequal in
their turn, and different from what they were intended to be.

[Illustration: Plate IV.]

69. =Biting with Stopping-out.--One Point.=--In biting with
stopping-out, it is the biting itself, and not the