of yellow, yellow-red, and hyacinth-red; these, by the admixture of alkalis, pass to the culminating point, and even beyond it to blue-red.
530.
No instance of a culmination on the minus side has come to my knowledge in the mineral and vegetable kingdoms. In the animal kingdom the juice of the murex is remarkable; of its augmentation and culmination on the minus side, we shall hereafter have occasion to speak.
XL.
FLUCTUATION.
531.
The mutability of colour is so great, that even those pigments, which may have been considered to be defined and arrested, still admit of slight variations on one side or the other. This mutability is most remarkable near the culminating point, and is effected in a very striking manner by the alternate employment of acids and