ficient size to conceal the disks from the class have it held in front of the wheel while the disk which conceals the combination is removed, the nut screwed to place and the disks put into rapid rotation; then order the card taken away and ask the class what color they see, still continuing the rotation.
The correct answer should be broken green-yellow, and not a shade of green-yellow, a broken yellow-green, a tint of yellow or a yellow shade; for there is but one true name and that should be stated. Definite expressions of color are as possible as the terms used regarding other scientific subjects, and should be encouraged.
Much interest can be inspired and valuable instruction imparted to the children by experiments with the color wheel, but whenever color analysis is the object in view, if disks of more than one of. the standard colors are used in the same combination they must be of colors adjacent to each other in the spectrum.
For example, if a blue and a yellow disk are united and placed in rotation the result may be a blue gray, a yellow gray, or perhaps very nearly a neutral gray, because blue and yellow are so nearly complementary to each other. But a nomenclature of the resulting color effect expressed in terms of blue and yellow is not of practical value, because it is evident that in the analysis of a gray-blue, yellow has no logical place. If in an attempt to match a color which seems to be a broken blue, something else besides the blue, white and black is required, it must be either green or violet, i. e., one of the two standard colors adjacent to the blue in the spectrum. In other words, every color in nature is a spectrum color, i. e., either a pure spectrum color, a tint or a shade of a spectrum color, or a broken spectrum color. Hence every color can be matched, and therefore analyzed by the combination of one disk of a standard color with a white disk, a black disk or both, or else by two adjacent spectrum standards with white and black or both.
There are many combinations of disks outside the limitations
