Halleck says: Every time we enter a street car we see different types of people, and there is a great deal to be noticed about each type. Every human countenance shows its past history to one who knows how to look. . . . Successful gamblers often become so expert in noticing the slightest change of an opponent's facial expression that they will estimate the strength of his hand by the involuntary signs which appear in the face and which are frequently checked the instant they appear.''

Of all classes, perhaps artists are more apt to form a clear cut image of the features of persons whom they meet—particularly if they are portrait painters. There are instances of celebrated portrait painters who were able to execute a good portrait after having once carefully studied the face of the sitter, their memory enabling them to visualize the features at will. Some celebrated teachers of drawing have instructed their scholars to take a sharp hasty glance at a nose, an eye, an ear, or chin, and then to so clearly visualize it that they could draw it perfectly. It is all a matter of interest, attention, and practice. Sir Francis Galton cites the instance of a French teacher who trained his pupils so thoroughly in this direction that after a few months' practice they had no difficulty in summoning images at will; in holding them steady; and in drawing them correctly. He says of the faculty of visualization thus used: "A faculty that is of importance in all technical and artistic occupations, that gives accuracy to our perceptions, and justice to our generalizations, is starved by lazy disuse, instead of being cultivated judiciously in such a "way as will, on the whole, bring the best return. I believe that a serious study of the best means of developing and utilizing this faculty, without prejudice to the practice of abstract thought in symbols, is one of the many pressing desiderata in the yet unformed science of education."