strokes on plate 20 are so well defined that it hardly seems necessary to
describe them. For a short piece of chalk is used, the side of the chalk giving
the width of the line. At 2 the stroke is similar, the accent being at one end
of the chalk. At 3 the stroke is slightly curving, the chalk being placed
vertically, and the accent being upon the upper end of the chalk. No. 4 is
drawn by placing the chalk vertically upon the board, drawing it downward very
quickly and twisting it to the horizontal position. Apply these strokes in
sketching the lobster. First use stroke 3, then touches like 2; afterward
strokes 1 and 4 for details.
No. 5 indicates the
strokes first used in sketching the shells. In drawing the outside of the
nautilus, use a long piece of chalk and with a curving stroke accented with the
end, form the outline. With strokes similar to those at 2, sketch the light
streaks in the shell, and add dark details with charcoal. Use the tip of the
finger in softening the tones here and there.
In drawing the
section, sketch first the spiral curve, then the blended strokes connecting the
outer with the inner curves of the spiral, and add charcoal for shadows.
The oyster shell is drawn by the use of the
lower stroke at No. 5. Make the stroke, accenting a little at the left end of
the chalk; then reverse the stroke, accenting with the right end, and add
details with chalk and charcoal.