PREFACE COLOR HAS been used by nature lavishly, purposefully, and effectively since the creation of our earth. Since hisown creation, man has used it more or less lavishly, purposefully, and effectively. Primarily he has made use of it because he likes it, has been pleasantly fascinated by it, and has found it to be an agreeable companion. Recently, with general advances in science, man has found color to be a valuable assistant in the performance of his daily work. In the history of man, color has always been and always will be associated with various arts, but its associations have become widened with the advance of civilization until today it is recognized as a great natural force, an important and indispensable element of our daily lives. Through its power to influence human be- havior, it is working every day for the benefit ofmankind all over the earth. Its usefulness as a guide to information is beingemployed by a multitude of scientists, investigators, and other seekers after facts in many fields. As its qualities are recognized, better understood, and more widely and intelligently applied, colormay help to effect a change in the nature of humanity. Ifthat is possible, it can be instrumental in diminishing mans most unnatural and unprofitable traits and increasing the better ones. At any rate, since it is at this moment a very important element of life and is contributing tremendously to the progress of humanity, to find out as much as can be known about it is desirable and profitable. While man has observed much about color, the various con- clusions that he has reached are not necessarily facts. Man will continue to discover truths about color and other things as he continues to search for them by observing, experimenting, and reasoning. Ideas about scientific matters are subject to change as new observations and discoveries are made. Color has been an element of life since the creation, but the