VIBRATION
of a cool overtone painted freshly into a warm undertone, care being taken not to mix or blend the two coats and not to cover up completely the undertone, rather letting it show through brokenly all over the canvas; the vibration being secured, naturally, by the separate play of the warm and the cold notes. Neither alone would accomplish this purpose, nor would the neutral gray that would result from a too thorough mixing of the tones in the final brush-work.
This method has first of all the great advantage of being thoroughly logical; for in nature herself the undertones are represented by the local color of the various units—leaves, grass, rocks, and good rich earth; and these are always warmer and more vivid in color than the lights dropped upon their surfaces by the over-arching sky. But the method
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