all the phases of the biting-in.

I notice that the acid does not act on certain parts of your work; you
will find out soon enough what that means.

36. =Treatment of the Various Distances.=--"I am thinking just now of
what you told me in regard to the background:--that more work ought to
be put into it than into the foreground."

Nothing, indeed, is simpler. You understand that the background, which
is bitten in quite lightly, must show very delicate lines, while in the
middle distance and in the foreground the lines are enlarged by the
action of successive bitings. When it comes to the printing, the
quantity of ink received by these various lines will be in proportion to
the values which you desired to obtain, and in the proofs you will have
a variety of lighter or stronger tones, giving you the needed gradations
in the various distances. It follows from this that, if you had worked
too sparingly on the distances which receive only a light biting, you
could not have reached the value of the tone which you strove to get,
and if you had worked too closely on those parts which require continued
biting, you would have had a black and indistinct tone, because the
lines, which are enlarged by the acid, and consequently keep approaching
one another, would finally have run together into one confused mass,
producing what in French is called a _creve_ (blotch).

In an etching the space between the lines must be made to serve a
purpose; for the paper seen between the black strokes gives delicacy,
lightness, and transparency of tone.

37. =The Creve.--Its Advantages and Disadvantages.=--In very skilled
hands the _creve_ is a means of effect. If you wish to obtain great
depth in a group of trees, in a wall, in very deep shadows, you will
risk nothing by intermingling your lines picturesquely and biting them
vigorously. In this way you can produce tones of velvety softness, and
at the same time of extraordinary vigor. Similarly, you may strike a
fine note by means of running together several lines which, if
sufficiently bitten, will form but a single broad one of great solidity
and power. It is, indeed, only the exaggeration of this expedient,
which, by unduly enlarging the limits of the broad line just spoken of,
and thus producing a large and deep surface between them, constitutes
the _creve_ properly so called; the printing ink has no hold in this
flat hollow, and a gray spot in the proof is the result. I have warned
you of