the effect of a change in some of the factors of the situation. Learning, however, continues through all the trials in spite of the shifts.

c. The correlation coefficients between average speed on the first 5 trials and that on the last 5 trials in the o° position, between average speed in the o° position and that in the rotated positions, and between average speed in either the o° position or rotated positions and that without the mirror, are high.

d. The correlation coefficients between ability to read mirror script and ability to handle the maze in any position are zero or small and negative.

e. The correlation coefficients between ability to handle the maze in any position, ease of making the shift from one position to another, gain from first to last trials and other measures of success on the maze and intelligence test scores (Army Alpha) are low, approximating zero. Similar coefficients between the various measures of success with the maze and scholastic standing are low and negative, but uniformly higher than those with intelligence test

scores.

A New Differential Color Mixer and Its Applicability. E. B. TWITMYER and S. W. FERNBERGER, University of Pennsylvania. The apparatus is constructed with a double shaft,-one inside the other. The outer shaft is attached to one color and to one of the pillars; the inner shaft is attached to the other color and to the other pillar. A spiral groove is cut in the outer shaft, in which engages a pin attached to the inner shaft. In this way the relation between the two shafts, and thus the relative amounts of color in the mixture, may be changed rapidly while the apparatus is revolving. Outer shafts are supplied with grooves of different pitches, -one for moving the colors through 100 per cent. for demonstration purposes; the other for moving the colors through 50 per cent. (and therefore with the possibility of finer gradations) for purposes of research. A direct reading scale indicates the relative position of the colors.

Preliminary experiments with this apparatus for obtaining the difference-limen for greys indicate its usefulness for the procedures either of the haphazard arrangement of the method of just perceptible differences or of the method of constant stimuli. It is possible to obtain 350 judgments,—50 judgments on each of seven pairs of stimuli,—in about three hours' time. The curves thus obtained are relatively of the form of the phi gamma hypothesis.

A New Type of Color-Mixer. PAUL THOMAS YOUNG, University of Illinois.

Stationary color discs may be mixed by means of rotating mirrors. Several types of rotating mirror have been tested and two, especially, have proved satisfactory: (1) Parallel mirrors rotated between the eye and the discs about an axis from the eye to the center of the discs. (2) A single plane mirror, set firmly at an angle to the axis of rotation, arranged so that the stationary discs may be seen in reflection.

Color surfaces for use with the new style color mixer must be arranged in special double-sectored discs in order to give a uniform color field. Other arrangements of color surfaces yield interesting results.

Stationary discs have several advantages over rotating discs. Continuous changes of color and light may be made easily and with an indefinite number of discs. Adjustment of the apparatus is simple and economical of time.

An Illuminated Perimeter with Campimeter Features. GERTRUDE RAND, Bryn Mawr College.

This instrument was devised in response to a request by the American Ophthalmological Society for a feasible means of illuminating the perimeter arm with light of a good intensity and quality, so that every point on the arm in any meridian in which it may be placed shall receive equal intensities of light. Intensity and quality of illumination are, however, only two of the factors which influence the results of the perimetric determination. In devising the instrument to be described in this paper it has been our purpose to provide a control also of other factors which are of importance to the work of the office and clinic.

By a sufficiently wide variation of intensity alone the fields of color sensitivity may be made to have almost any breadth within the field of vision, to differ radically in shape and even to change or reverse their order of ranking as to breadth. The limits for pigment stimuli may be either interlacing or concentric in the order from widest to narrowest of red, blue and green; or of blue, red and green, depending upon the intensity of light falling on the perimeter arm. Without great precision in the control of intensity it is obvious that reproducibility of result can not be obtained and little. significance can be attached to extent or shape of field, to order of ranking as to breadth of field, or to any variations from time to time or from person to person in these important features.

Other special features of the instrument are a carefully standardized control of brightness of preëxposure and surrounding field; a provision for an accurate control of fixation both for the normal eye and for the eye having a central scotoma; a device for the mapping of a central scotoma; a tangent screen for the mapping of the blind spot and paracentral and peripheral scotomata, which can be readily attached and removed from the stimulus carriage; etc. The Effect of Variations of Intensity and Composition of Light and Size of Visual Angle on Functions of Importance to the Working Eye. C. E. FERREE, Bryn Mawr College.

The benefit of increase of intensity of illumination is shown for the following functions of importance to the working eye:-acuity, power to sustain acuity, speed of discrimination and speed of adjustment of the eye for clear seeing at different distances. Wide ranges of change of illumination were used. The effect was measured both on normal eyes and eyes with slight errors in refraction of a type and amount of frequent occurrence in the corrected eye. The benefit of the increase was found to be considerably greater in case of these slight defects than for the normal eye. A comparison is made of the effect of increase of intensity of illumination and increase in size of visual angle. The question of the most favorable intensity of illumination of test charts for different test purposes is discussed. The importance of testing the neglected aspects of acuity: speed and power to sustain, in relation to diagnosis, vocational selection, and hygiene or welfare work on the eye is demonstrated. A comparison is made of the sensitivity of acuity, speed of discrimination, speed of adjustment of the eye for clear seeing at different distances, and power to sustain acuity, as test features for picking up small differences in the functional power of the eye.

The investigation is also extended to include the effect of variations in the composition of light on acuity, power to sustain acuity, and speed of discrimination. Two intensities of light at seven points in the spectrum were used. The relative importance of resolving power of the refracting media and resolving power of the retina is discussed in relation to the effect of changes in composition of light on acuity, speed of discrimination and power to sustain acuity.

Practical Logic and Color Theories. CHRISTINE LADD-FRANKLIN, Columbia University.

The psychologists, when they discuss reasoning at all (and some of them hardly give it passing mention), take the ground that the

kind of reasoning that interests them is something very different from the cut and dried formulas of the logician. The reason for this quarrel between two honorable branches of science is simply, of course, that the psychologist has the inveterate habit of including in his term reasoning the search for what I have called the "adequate" premises-what is half the battle, of course, when one is engaged in thinking out a solution to real difficulties. The pure logician, on the other hand, cares nothing for this aspect of the matter he is concerned only with the validity of structures of premises. I propose to use the term practical logic, in a technical sense, for the psychologist's logic, and to call that of the logician theoretical logic, or pure logic. This simple device of giving two names to two different things ought to have the effect of modifying the contemptuous terms in which the psychologists sometimes discuss the logicians.

I must first urge the adoption of certain reforms in color terminology which I have long been advocating and which are indispensable to a thoroughgoing discussion of this subject,-namely, chroma and achroma for the two kinds of sensation which the word color now covers ambiguously; chromaticity and achromaticity for the degree in which these two types of sensation are present in a complex color experience; and other equally useful changes.

Why should not the scientist, whose constant occupation is practical reasoning, devote some time, now and then, to polishing up the tools of his trade? Why should he not make a special study, when occasion offers, of the great quagmires of bad reasoning that, in various fields, lie behind him? And it is exactly the psychologist who will have the best material for this study. It is safe to say that there has never been a subject of scientific research that has offered such a good field for studies of this kind as does the subject of color. Both the old theories and the new-both the current theories and the non-current-are rich in not only common errors of logic but far more, of course, in sins against the fundamental principles (axioms, as G. E. Müller calls them) of the neuro-psychic correlation. And it is the mistaken theories of color which have high pedagogical value in sharpening up the wits of the intending

reasoners.

Psychology in Relation to Social Work. RICHARD C. CABOT, Harvard University.

[No abstract.]

The Biology of Sanity. STEWART PATON, Princeton University. 1. Sanity and Insanity, like words health and disease, are relative terms requiring constant revision.

2. Useful occasionally to try and describe these conditions as this gives indication of character of methods used in the investigation of vital phenomena.

3. Unfortunately, value of synthetic methods not appreciated to same extent as value of analytical methods in the study of the personality.

4. Important for practical as well as theoretical reasons that both methods should be used.

5. Importance of both methods, illustrated by case records. 6. In order to understand conditions described as "sanity," we have to consider organization of the body as well as mind.

7. Organization of the sound body: (a) Provision for drainage of energy manufactured in well-coördinated movements. (b) Energy liberated to meet critical situations adequate, but not in excess, of that which occasion demands. (c) Proper adaptation of instinctive activities. (d) Satisfactory compensatory processes for existing physical defects. (e) An efficient executive department.

8. Organization of the sound mind. (a) Extends range of adaptability by supplementing physical organization. (b) Supplies sense of completeness and accomplishment. (c) Appreciation that “activity is the cardinal fact of life." (d) Recognizes life as a process and not a state of adjustment. (e) Coördination of activities does not interfere with illative capacity. (f) Well-organized judicial department.

9. Accurate observation of efforts made to adjust life are often of more scientific importance than the data obtained by any of the artificial systems devised for testing intelligence.

10. Results of "Intelligence-Tests" should always be checked up by comparison with actual life experiences.

Psychology and Psychiatry. SHEPHERD IVORY FRANZ. St. Elizabeth's Hospital, Washington, D. C.

Perhaps the greatest difficulty in the relations between psychology and psychiatry is the relative ignorance of psychologists and psychiatrists of the methods and facts of the other discipline. Another is the fact that both have frequently identified psychiatry or psychology with the work of some single man-and usually one with whom they disagree emphatically. The two borderline fields.