Throughout the course of the experiment, except in the advanced stage when more complex states were under consideration, sounds, colors, odors, simple figures, and tactual surfaces were used. In the late stage of the investigation sentences and pictures more or less morally and æsthetically suggestive served to furnish for study the complex feeling-states. The progress of the investigation divides itself naturally into the following four distinct parts. I. From every experience of each individual the investigator sought to obtain from the subject's own introspection at the time as adequate a description as possible of the particular feeling provoked by the chosen stimulus. The feelings studied in this first period of the investigation are entirely those which heretofore have not been at all classified except in terms of the objects which call them forth. Part I is concerned with single stimuli affecting only one kind of sense-organ, visual, tactual, auditory, or olfactory as the case may be. Two requests were made of each subject, viz: (_a_) To describe as clearly as possible how the particular experience _felt_. (_b_) To report always all the accompanying physiological or physical processes which seemed to _mean_, to result from, or apparently only accidentally to accompany the stimulus judged by him to have a feeling-tone. The work of the experiment covers a period of two years, and fortunately several of the subjects were available for the whole period. No subject was used for more than two hours each week. In the preparatory training with sensations from only one sense-organ, the range of colors, odors, etc., was chosen as follows: Twenty colors, and as many tactual surfaces, etc., were presented in turn, and each subject was requested to make his judgment as to the relative degree of agreeableness or disagreeableness of the feelings arising in the several cases. The scale of numbers from 1 to 7 served in the traditional way to indicate approximately the hedonic value of the feeling-tones, 1 signifying highest degree of pleasure, 2 very pleasant, 3 slightly pleasant, 4 indifferent, 5 slightly unpleasant, 6 very unpleasant, and 7 the highest degree of unpleasantness. Though the personal differences were in some cases rather striking, the individual subject from day to day showed a relatively constant standard. This was done in order simply to be able to choose approximately the stimulus in the individual case likely to call up the _kind_ of feeling one wished to study more in detail, and thus facilitate the progress of the investigation. In this preliminary stage pleasant or unpleasant seemed to the subjects more or less an exhaustive account of these faint feelings. This was a means of eliminating practically indifferent shades, as there is here no special interest in the psychology of color as such. * * * * *