If the yellow tint is used, let it become quite dry and then wash it over with a large brush and _clean_ water; then, as in the flower painting, soak up the water with blotting-paper; the blotting-paper must also be quite clean. While the paper is damp, not wet, begin with a blue tint—a light wash of cobalt will give it—and put in the sky _in a flat tint_; bring the same color down all over your sketch except in the high lights. The blue tint gives atmosphere and distance. Let your paper again become quite dry, and then wash it over as before, in clear water. The process of laying on color and lightly washing over it afterward should be repeated several times, “and the result will be a transparent aerial tone.” Keep your extreme distance bluish, your middle distance warmer in tone, but not too strong, and the principal objects in your foreground strong. Leave out small objects, and with light and shade seek to obtain the effect. Keep your colors pure or your sketch will be dull. Contrast has much to do in producing strength and character. Phillips says that, “in aiming at opposition of color, we must select that which gives force to the foreground, and consequently communicates the appearance of air in the distance. Thus, if the general tone of the light be warm and yellow, we should have blues and purples in the foreground; if the lights be cool, reds and yellows in the foreground give atmosphere to distance, as neither of these colors in a positive state is found in the middle or remote distance.” The three principal contrasts are blue opposed to orange, red to green, and yellow to purple; and “a good first lesson in sketching in color will be to put in your shadows with color opposite to the object in light; and by carrying out this principle of opposition throughout the scale you will obtain an endless variety of contrasts.” It is the general rule in most painting to have cool shadows to warm lights, and warm shadows to cool lights. We all know that a _green_ picture is very disagreeable, and although a green field _is_ green, it must not be made intensely so. An untrained eye will not see how nature tones down the vivid color with shadows, and softens it with the atmosphere; but when the eye has learned to look at nature in the right way this difficulty will be overcome. Howard says, “green must be sparingly used, even in landscapes, whose greatest charm consists of vegetation.”