out what may further be deduced from these phenomena, and to show what other facts they may be connected with.
XLIII.
FIXATION.
545.
Mutable as we have hitherto found colour to be, even as a substance, yet under certain circumstances it may at last be fixed.
546.
There are bodies capable of being entirely converted into colouring matter: here it may be said that the colour fixes itself in its own substance, stops at a certain point, and is there defined. Such colouring substances are found throughout nature; the vegetable world affords a great quantity of examples, among which some are particularly distinguished, and may be considered as the representatives of the rest; such as, on the active side, madder, on the passive side, indigo.
547.
In order to