st was dry it was gone
over with a thin wash of glue-water, and sharp "silver" sand thrown
on; when dry, coloured by staining it with various oil colours (not
tube), and some few powder colours--blue-black, yellow ochre, Vandyke
brown, celestial blue (cheap), burnt sienna, etc, thinned with turps,
afterwards touched up, when dry, with touches of tube colours, smartly
and cleanly put on. This would be the treatment and colouring for
greyish-brown or yellowish-grey smooth, dry-looking rocks, sandstones,
etc.; and by a little alteration of tint and treatment in places, would
imitate the various slates.

For chalk and limestone, mix plaster and sand with the whiting and lay
it on thickly, not throwing on sand, as a final operation. Colours, of
course, are different here, more bright and light green predominating;
but the colouring of the rockwork, etc, to imitate the various kinds of
rocks required, is only to be learned by experience; in point of fact,
to colour rocks in an effective manner is really the work of an
artist, for it is requisite to know the properties of colours, and to
"scumble" and "stipple" or "glaze" one colour over another to get
"depth." A few hints may, however, help out the tyro.

For rough sea rocks, after sanding and glueing, go over the rockwork
with a mixture of chrome yellow and Prussian blue, mixed with oil and
turps, the blue predominating; touch up the points with white, and
allow it to dry. The next day deepen the shadows with Brunswick black,
"stippling" lightly the remainder of the rock with the same. Arrange
sea-shells and sea-weed, here and there, where the mounted subject
allows of this treatment. This is a shining dark bluish-green and
brown rock, suitable for sea-gulls, divers, etc.

For rough grey land rock, paint over all with lamp-black in powder,
mixed with plaster of Paris, and touch up the points with oil white.
When the work is quite dry, go over all with a glaze of Prussian blue
mixed with Brunswick black. Fit up with ferns, grass, and golden
lichens on the points, or in the hollows. This makes a greyish rock
with no gloss, and is suitable for owls and similar birds.

For rough sandstone rock, paint over with chrome yellow and a very
little blue mixed with oil white, the latter predominating; dust over
on the points with red sand, touch up the hollows with Brunswick
black, suffer to dry, and then go over all with a very little rose
pink or vermilion, worked up in turps with