follow it;
noticing first, after abstract lines, the imitable forms of the four
elements, of Earth, Water, Fire, and Air, and then those of animal
organisms. It may be convenient to the reader to have the order stated
in a clear succession at first, thus:--

1. Abstract lines.
2. Forms of Earth (Crystals).
3. Forms of Water (Waves).
4. Forms of Fire (Flames and Rays).
5. Forms of Air (Clouds).
6. (Organic forms.) Shells.
7. Fish.
8. Reptiles and insects.
9. Vegetation (A.) Stems and Trunks.
10. Vegetation (B.) Foliage.
11. Birds.
12. Mammalian animals and Man.

It may be objected that clouds are a form of moisture, not of air. They
are, however, a perfect expression of aerial states and currents, and
may sufficiently well stand for the element they move in. And I have put
vegetation apparently somewhat out of its place, owing to its vast
importance as a means of decoration, and its constant association with
birds and men.

Sec. XVIII. 1. Abstract lines. I have not with lines named also shades
and colors, for this evident reason, that there are no such things as
abstract shadows, irrespective of the forms which exhibit them, and
distinguished in their own nature from each other; and that the
arrangement of shadows, in greater or less quantity, or in certain
harmonical successions, is an affair of treatment, not of selection. And
when we use abstract colors, we are in fact using a part of nature
herself,--using a quality of her light, correspondent with that of the
air, to carry sound; and the arrangement of color in harmonious masses
is again a matter of treatment, not selection. Yet even in this separate
art of coloring, as referred to architecture, it is very notable that
the best tints are always those of natural stones. These can hardly be
wrong; I think I never yet saw an offensive introduction of the natural
colors of marble and precious stones, unless in small mosaics, and in
one or two glaring instances of the resolute determination to produce
something ugly at any cost. On the other hand, I have most assuredly
never yet seen a painted building, ancient or modern, which seemed to me
quite right.

Sec. XIX. Our first constituents of ornament will therefore be abstract
lines, that is to say, the most frequent contours of natural objects,
transferred to architectural forms when it is not right or possible to
render such forms distinctly imitative. For instance, the line o