^02 



SCIENCE, 



[X. S. Vol. IX. No. 235. 



means farness of the observer from the 

 things viewed, while definiteness of detail 

 in the individual object means nearness in 

 point of view. In the given case there is, 

 relatively to the number of discernible ob- 

 jects, an abnormal distinctness, or, rela- 

 tively to their definition, an abnormally 

 great number of objects. Adoption of the 

 one as criterion will lead to an underesti- 

 mation of size ; adoption of the other will 

 result in an overestimation of distance. 

 The former actually obtains, and for this 

 reason as it appears. 



The dominant factor of the change in 

 character of visual objects here is the in- 

 creased distinctness of them at any given 

 distance — the greater definiteness of line 

 and shadow, the elaboration of detail. Such 

 distinctness of form means in general near- 

 ness of the object to the observer. Now the 

 near object in order to be seen as a total, a 

 unity, must be comparatively small. The 

 arrangement of a garden plot cannot be 

 grasped while one walks along its paths as 

 when viewed from a window overlooking 

 it ; the course of a river can be apprehended 

 only when seen from some neighboring 

 height. The same holds true of smaller as 

 of larger groups of elements — the observer 

 must step back in order to get the general 

 effect — i. e., to appreciate the factors as a 

 total object. The more complex or grander 

 the proportions of an object the farther 

 away must be the point of view from which 

 it can be grasped as a unity. If, then, it 

 is so to be apprehended while yet near to 

 the observer its parts must be small and 

 simple. In the case in question the effect 

 of the new glasses was thus to increase the 

 definiteness of detail in visual objects, while 

 these objects were still regarded as totals, a 

 combination directly tending to produce 

 that sense of smalluess in the individual 

 object which was actually noticed. 



Another fact points in the same direction. 

 Of curved surfaces a large radial extent 



can be seen distinctly by the myopic eye 

 only when the object is a small one, and, 

 therefore, not greatly affected by the paral- 

 lactic angle. Of equally distinct objects, 

 therefore (which in the two cases will be 

 at different distances), the myopic subject 

 sees less curative-extent than the normal ; 

 or, for two equally distinct objects in the 

 mj'opic field of view (which are, therefore, 

 at the same distance from the eye) gi'eater 

 visible extent of curvature means smallness 

 of size. By the use of the new glasses the 

 extent of visible curvature was thus in- 

 creased, while the distinctness of the objects' 

 details remained unaffected. This influ- 

 ence, therefore, co5perated with the pre- 

 ceding to produce the feeling of unnatural 

 smallness in the nearer objects of vision. 



b. The change in relative curvature- 

 extent visible from the point of distinct 

 vision appears to have been active in the 

 production of another perspective illusion, 

 the exaggeration of curvature in objects 

 bounded by convex surfaces. The cheek 

 or brow of a person, for example, appeared 

 to bulge out unduly in the middle, and 

 there was a constant tendency to put out 

 the hand and test by touch the accuracy of 

 of the sight perception. In the myopic eye 

 the jjoint of view of distinct vision lies so 

 near to its object that for any given group 

 of things the perceived curvature extent is 

 small in comparison with that visible to the 

 normal eye. In objects beyond the range 

 of distinct vision, when such are not over- 

 looked and referred to the unnoticed back- 

 ground, the curvature gradations are ob- 

 scured and the myopic eye must depend 

 vipon other cues for its interpretation of 

 convexity degree. It reinforces the percep- 

 tion by contributed curvature elements. 

 When the finer gradations of curvature are 

 restoi'ed to sight by the stronger glasses the 

 contributed emphasis appears to be con- 

 tinued, with the result of an apparent ex- 

 aggeration of curvature. I have not had 



