Displacement-effect of eccentric circles

Abstract

The problems of displacement-effect of eccentric circles, as against that of concentric circles, were studied experimentally. At first it was found that, as the inner circle which had evoked the maximum positive displacement-effect in concentric circles was moved in any direction from its concentric position, the displacement-effect diminished gradually with the increase in the distance between the center of the inner circle and that of the outer (the degree of eccentricity) ; and that upon contact, the displacement-effect became either zero or negative. Also, by moving the inner circle that had displayed maximum negative displacement-effect in concentric circles, we found the same tendency in reverse direction. However, displacement of the inner circle, in the case of “neutral” concentric circles which had evoked neither positive no negative displacement, had almost no effcet, the value being zero or near zero constantly. Comparing concentric and eccentric displacement-effects in various situations : 1) with the minimum gap between the outer circle whose radius was 90 mm and the inner circles kept constant at 12 mm, 2) with the circles inscribed, the following results were obtained : the absolute displacement of the inner circle was definitely larger in the case of concentricity, while when the circles were inscribed the displacement was zero or negative, so for as the present experiments could reveal. If that portion representing the greatest distance between the inner and outer circles in both cases can be considered as the determinant of the displacement-effect, the maximum positive displacement of both concentric and eccentric circles and the peak of the decreasing tendency in negative displacement of inscribed circles were both found to occur at the same point, i.e., when the maximum gap between circles was 30 mm. It may be possible to deduce from these results that displacement of the inner circle in eccentric circles including inscribed circles depends solely upon the absolute distance between the circles. It therefore seems somewhat questionable to explain this displacement-effect, as most of investigators have tried, by “figure and ground”relationship. By measuring the field-forces formed inside and outside the both circles in accordance with Köhler's-electric field hypothesis, we might clarify these problems more precisely in future.