Page:A color notation (Munsell).djvu/92

 (135) The transparent envelope is thus divided into one hundred compartments, which provide for ten steps of value in each of the ten middle colors. Now, if we cut open this envelope along one of the verticals,—as, for instance, red-purple (RP), it may be spread out, making a flat chart of the color sphere (Fig. 22).

(136) A cylindrical envelope might be opened on any desired meridian, but it is an advantage to have green (G) at the centre

of the chart, and it is there- fore opened at the opposite point, red-purple (RP). To the right of the green centre are the meridians of green- yellow (GY), yellow (Y), yellow-red (YR), and red (R), all of which are known as warm colors, because they contain yellow and red. To the left are the meridians of blue-green (BG), blue (B), purple-blue (PB), and purple (P), all of which are called cool colors, because they contain blue. Green, being neither warm nor cold of itself, and becoming so only by additions of yellow or of blue, thus serves as a balancing point or centre in the hue-scale.

(187) The color score presents four large divisions or color fields made by the intersection of the equator with the meridian of green. Above the centre are all light colors, and below it are all dark colors. To the right of the centre are all warm colors, and to the left are all cool colors. Middle green (5G?) is the centre of balance for these contrasted qualities, recognized by all