130. The best method of describing and distinguishing these
value-contrasts will be to use the value-names in a form of fractions.
For example, Lt/D would mean a contrast of Dark on Light, D/Lt would
mean a contrast of Light on Dark, Wt/Blk would mean a contrast of Black
on White. That is to say, White is subdivided or crossed by Black. When
we wish to describe several contrasts in combination, we set the value
of the ground-tone above the line, always, the value of the tone or
tones put upon it below, thus:—
Lt
-----------
Wt Blk
This formula means, spots of White and Black on a ground of Light.
Lt
--------------
Wt Blk
---
M
This formula means spots of White and Black on a ground-tone of Light,
with a spot of Middle on the White, the Middle being altogether
separated from the Light by the White.
There is no definite thinking except in definite terms, and without
some such terminology as I have devised and described, it will be
impossible to enter upon an experimental practice in value-relations
with the hope of definite results. With definite terms, however, we can
take up the practice in value-relations with a good chance of learning,
in the course of time, all that there is to be learned.