haps in the direction of the inventive adaptation of
analogous principles. But in art the question is complicated by human
feeling and association, and her strongest appeal is to these, and by
these, and as yet we do not seem to have any terms or equivalents
precise enough to describe, or any analysis fine enough to discover
them.

[Extension]

The next consideration in spacing we may term _extension_. This bears
upon all surface design, but more especially upon the design of patterns
intended to repeat over a large surface, and not specially designed for
particular spaces. It is a great question whether any design can be
entirely satisfactory unless it has been thought out in relation to some
particular extent of surface or as adapted to some particular wall or
room. Modern industrial conditions preclude this possibility as a rule,
and so the only sure ground, beyond individual taste and preference, is
technical adaptability to process or material. We should naturally want
to give a different character to a textile pattern, whether printed or
woven, and intended to hang in folds, from one for flat extension as a
wall-paper; and a different character again to such designs intended for
extension horizontally from those intended for vertical space alone.
Floor patterns, parquets and carpets, for instance, naturally demand
different treatment from wall patterns, as those orders of plants in
nature which cling and spread on the flat ground differ from those which
grow high and maintain themselves in the air, or climb upon trees. The
rule of life--_adaptability_--obtains in art as in nature, and, beneath
individual preference and passing fashion, works the silent but real law
of relation to conditions. This again bears upon the choice of scale,
and differentiates the design of dress textiles from furniture textiles,
and the design of varied surfaces and objects, which, while demanding
their own particular treatment, are brought into general relation by
their association with use and the wants of humanity.

[Illustration (f077a): Extension: Surface Pattern Motives Derived from
Lines of Structure.]

[Geometric Structural Plans, etc.]

The law governing extension of design over surface is again geometric,
and our primal circle and square are again the factors and progenitors
of the leading systems which have governed the d