The London, Edinburgh and Dublin philosophical magazine and journal of science . ely. Sincethe movements of the lines of force are at each point normalto the ellipse, no flux will cross the major and minor angles AOB and COD show the incidence of the linesof force upon the right and left retinas. It is evident thatmore lines of force cut the nasal halves of the retinae thanthe temporal halves. It is also apparent that the optic nerveslie almost parallel to the normal of the elliptic coil, and thatthey therefore will be cut by comparatively few lines offorce. The solenoid was made ligh
The London, Edinburgh and Dublin philosophical magazine and journal of science . ely. Sincethe movements of the lines of force are at each point normalto the ellipse, no flux will cross the major and minor angles AOB and COD show the incidence of the linesof force upon the right and left retinas. It is evident thatmore lines of force cut the nasal halves of the retinae thanthe temporal halves. It is also apparent that the optic nerveslie almost parallel to the normal of the elliptic coil, and thatthey therefore will be cut by comparatively few lines offorce. The solenoid was made light-proof by fastening strips ofrubber insulator over the joints between the segments of thecoil and by covering the top with felt. The lower end intowhich the head of the observer was placed was closed bystuffing felt wadding around the neck of the observer. Sensations caused by a Magnetic Field, 195 Inasmuch as the series of ten observations did not requireordinarily more than ten minutes, the exigencies of fresh aircould safely be met. In determining the threshold, the field. was begun subliminally and gradually increased until theobserver signalled, by means of an electric light which heoperated with a button, that the visual sensation was justapparent. Although the field was gradually increased instrength by taking out resistance, the field was intermittentlymade and broken by a switch which was operated by anassistant. A pendulum of suitable length enabled theassistant to keep the switch closed for one second and openfor an equal length of time. The period of stimulation andthe intervening interval were thus kept tolerably the observation in which the stimulus was in-creased from subliminal to liminal, there occurred aninterval of a few seconds when the instruments were readand recorded. Inasmuch as three persons co-operated inthis part of the experiment, the work was done rapidly. Inthe second observation of the series, the stimulus was begunfar above th
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectscience, bookyear1840
