[3] This pure red, the union of orange and violet, is considered by the author the maximum of the coloured appearance: he has appropriated the term purpur to it. See paragraph [703], and note.—T.
[4] The bands or stripes in fig. 4, [plate 1], when viewed through a prism, exhibit the colours represented in [plate 2], fig. 5.
[XV.]
EXPLANATION OF THE FOREGOING PHENOMENA.
Before we proceed further, it is incumbent on us to explain the first tolerably simple phenomenon, and to show its connexion with the principles first laid down, in order that the observer of nature may be enabled clearly to comprehend the more complicated appearances that follow.
In the first place, it is necessary to remember that we have to do with circumscribed objects. In the act of seeing, generally, it is the circumscribed visible which chiefly invites our observation; and in the present instance, in speaking of the appearance of colour, as occasioned by refraction, the circumscribed visible, the detached object solely occupies our attention.