(163) In the construction of the color solid we saw that its scales were made of equal steps in hue, value, and chroma, and tested by balance on the centre of neutral gray. Any step will serve as a point of departure to trace regular sequences of the three types. The vertical type is a sequence of value only. It is somewhat tame, lacking the change of hue and chroma, but giving a monotonous harmony of regular values. The horizontal type traces a sequence of neighboring hues, less tame than the vertical type, but monotonous in value and chroma. The inward type connects opposite hues by a sequence of chroma balanced on middle gray, and is more stimulating to the eyes. (164) These paths have so far been treated as made up of equal steps in each direction, with the accompanying idea of equal quantities of color at each step. But by using _unequal quantities of color_, the balance may be preserved by compensations to the intervals that separate the colors (see paragraphs 109, 110). +Unequal color quantities compensated by relations of hue, value, and chroma.+ (165) Small bits of powerful color can be used to balance large fields of weak chroma. For instance, a spot of strong reddish purple is balanced and enhanced by a field of gray-green. So an amethyst pin at the neck of the girl’s dress will appear to advantage with the gown, and also with the Leghorn straw. But a large field of strong color, such as a cloth jacket of reddish purple, would be fatal to the measured harmony we seek. (166) This use of a small point of strong chroma, if repeated at intervals, sets up a notion of rhythm; but, in order to be rhythmic, there must be recurrent emphasis, “a succession of similar units, combining unlike elements.” This quality must not be confused with the unaccented succession, seen in a measured scale of hue, value, or chroma. +Paper masks to isolate color intervals.+ (167) A sheet of paper large enough to hide the color sphere may be perforated with three or more openings in a straight line, and applied against the surface, so as to isolate the steps of any sequence which we wish to study. Thus the sequence given in paragraph 160--Y 8/7, G 6/5, BG 4/3--may be changed to bring it on the surface of the sphere, when it reads Y 8/3, G 6/5, BG 5/5. A mask with round holes, spaced so as to uncover these three spots, relieves the eye from the distraction of other colors. Keeping the centre spot on green, the mask may be moved so as to study the effect of changing hue or value of the other two steps in the sequence. (168) The sequence is lightened by sliding the whole mask upward, and darkened by dropping it lower. Then the result of using the same intervals in another field is easily studied by moving the mask to another part of the solid.