Before speaking of the different kinds of edges, I will mention something of the harmony of colors, as in drawn edges the real harmonious combination of colors is of great influence on their beauty. The application of color in the art of marbling gives us certainly extraordinary freedom and a wide range to our fancy, but nevertheless there are certain principles or laws necessary to make the colors appear in an effective and beautiful way. Those tones of color which lie between yellow and reddish yellow are called warm, those between blue and the middle of reddish blue, cold colors. In the center lies red by its strength and effectiveness forming the dividing line between the warm and cold. To explain the principles of color harmony, the colors are divided into three groups, first, primary colors, second, secondary, and third, tertiary. Primary colors are those which cannot obtain their inherent purity by any mixture, namely red, yellow, blue, white and black. Secondary are those which are generated by a combination of two primary colors, for instance, orange, purple, green and grey. Tertiary, or broken colors, are those which are obtained by mixing two equally powerful secondary colors, for instance, brownish red, olive, slate grey, etc. In the harmony of colors luminosity and intensity play the main parts. The darkest color must occupy three times as much space as the lightest and the succession must be kept up in this way always taking into consideration the luminosity of the colors. Which colors must now be placed alongside one another to produce a harmonious effect? The laws for this are founded on the peculiarity of the power of man's vision. The eye, demands to be satisfied, an accord of primary colors. Red requires to annihilate one sided irritation the two primary colors, yellow and blue. The secondary green is obtained by a combination of yellow and blue, for that reason green is the color demanded by red to please the eye. But there must be a contrast of colors, for instance light red and dark green or dark red and light green must be brought together. The same thing is the case with other primary colors. The primary color yellow demands the secondary purple, blue, the secondary orange, the tertiary color olive, the secondary orange, brownish red and green, brimstone yellow and violet. The correct treatment of the shadow tone of a given color depends upon the knowledge of the laws of the annihilation of color effect. As in nature, a shadow is formed by obstructing the light, so in the technic of coloring the shadow is obtained by the annihilation of the light-color. By combination of a primary color with a harmonizing secondary color of equal strength, we obtain the right shadow tone of the first color. In this way, by experiments in mixing, the right shadow tones, which form in a multi-colored edge, the gradual transitions of primary colors can be easily detected. THE COMB MARBLE. THE COMB MARBLE.