[5] In this case, according to the author, the refracting medium being increased in mass, the appearance of colour is increased, and the displacement is greater.—T.
[7] Fig. 2, [plate 1], contains a variety of forms, which, when viewed through a prism, are intended to illustrate the statement in this and the following paragraph.
[XIV.]
CONDITIONS UNDER WHICH THE APPEARANCE OF COLOUR INCREASES.
We have seen in the foregoing experiments that all appearance of colour occasioned by refraction depends on the condition that the boundary or edge be moved in upon the object itself, or the object itself over the ground, that the figure should be, as it were, carried over itself, or over the ground. And we shall now find that, by increased displacement of the object, the appearance of colour exhibits itself in a greater degree. This takes place in subjective experiments, to which, for the present, we confine ourselves, under the following conditions.