The color photograph is found to be most useful in developing the color sense in children. The act of recognizing various colors and shades is educative. When we consider that all the effects of the color photograph are produced by combinations of the three primary colors we at once step into a realm of thought and observation that is boundless. The danger is that we may attempt too much with the abundance of material at hand and, by forgetting the limitations of the unformed mind, confuse instead of enlighten. It is well for the teacher to know the process by which the color photograph is produced, but young children who know little of the laws of light are not expected to understand it fully. In advanced classes the following will be found beneficial: A natural object is placed before a camera and a water screen is adjusted so no rays but the yellow may reach the photographic plate. A negative is thus obtained recording all the yellow that appears upon the surface of the object, whether it shows as pure yellow or in combination with other colors. With the camera and object in exactly the same position and another screen which absorbs all the rays but the red ones coming from the object, a negative of the red is obtained. A third negative of the blue in the object is similarly got, and we have an accurate representation of the form and all the colors of the object separated into red, yellow, and blue. From these negatives three half-tone plates are made upon copper. A half-tone plate is an acid etching produced by photographic process with fine lines crossing each at right angles so that the picture appears as a series of microscopic square points which decrease in size in the lighter portions of the plate. Red, yellow, and blue inks of the rarest quality are used in printing from these plates, with great care exercised as to getting the exact depth of color required for each. By placing a sheet of fine tissue paper beneath a plate printing red, the red is deepened, another sheet makes it more intense, and others are placed under the plate, if necessary, to get the rich red required to blend with the yellow and blue to make the exact reproductions of nature's colors which appear in the color photograph. The order of the printing is yellow first, and when this is thoroughly dry the red is laid on, and the blue a day later. As the color is nowhere a solid mass, but a series of points, one color does not hide another, but the three colors shine through and make the blendings which appear in the beautiful and delicate shades and tints of the color photographs. Do not manifest surprise when you find pupils wholly or partly color blind. The boy who cannot find a red marble in the grass will show by his conversation that red and green are the same to him. His is an extreme case, but there are many who are slow to name the primary colors and totally fail to recognize differences in tints.