. Physical researches on sensation [by] Frank Allen [and others]. ol. XI. of light is increased, the degree of exhaustion will undoubtedly begreater, and the maximum may be reached in the same or even in less time. Normal Persistency first persistency curveobtained was the normal. Asthis was the standard with whichcurves for abnormal conditionsof the eye were to be compared,the readings were taken withgreat care to avoid all sources oferror. The eye was allowed torest in diffused daylight for morethan ten minutes before eachreading. The values of thisseries of settings are given inT
. Physical researches on sensation [by] Frank Allen [and others]. ol. XI. of light is increased, the degree of exhaustion will undoubtedly begreater, and the maximum may be reached in the same or even in less time. Normal Persistency first persistency curveobtained was the normal. Asthis was the standard with whichcurves for abnormal conditionsof the eye were to be compared,the readings were taken withgreat care to avoid all sources oferror. The eye was allowed torest in diffused daylight for morethan ten minutes before eachreading. The values of thisseries of settings are given inTable I. They are also graphi-cally shown in Fig. 4, in whichordinates represent the persist-ence of vision for various partsof the spectrum in seconds, andabscissae are wave lengths. 1 NOF MAU CUR> E. 3 \ \ \ -025 \ \ 0 z00 \ \ GO \ / ; \ / lUio \ > \ / ^i^ ■ 0-^ r .4 3/^ 5 WAVE LENGTHS. 0 1 .60 .1 0 Fig. 4. To guard against error, observations with the eye in its normalcondition were frequently made to see if any change had taken Table I. Normal place. A series of such settings taken towards the latter part of theinvestigation is given in Table II. Their relation to correspondingreadings upon the original normal curve is indicated by X?> in Fig. No. 5.] PERSISTESCE OF VISION. 265 5. This curve, like the ones given by Nichols and by Ferr) in thepapers cited, shows that the persistence is least near the D line and
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