AMERICAN JOURNAL OF SCIENCE. 
[THIRD SERIES.] 
—————~o—_—_—- 
Arr. XXXI.—On the Duration of Color Impressions upon the 
etina ; by Epwarp L. Nicwots, Ph.D. — 
{Read at the Montreal meeting of the American Association for the Advancement 
of Science.] 
T is now more than half a'century since the publication of 
Plateau’s well known researches upon persistence of vision. In 
his.experiments the velocity was determined at which a revolv- 
ing disk with alternate black and white sectors began to 
present a homogeneous surface to the eye; and this rate was 
taken as the measure of the duration of the image formed upon 
the retina by the bright parts of the disk. Upon een 
red, yellow and blue sectors for the white ones, Plateau foun 
that the velocity necessary to this appearance of homogeneity 
Was not always the same, bei reatest when yellow 
alternated with black upon the rotating disk, and least in the 
eases in which the white sectors were replaced by blue ones. 
This reales dR the duration of the impression made 
the writers on Physiological Optics; and yet after fifty years. 
our knowledge of the manner in which the duration of the 
* i + . , . . * : 
sas Htescdegenat aed bcp poke des impressions produits par la lumiére 
t mann, Poggendorff’s Annalen, xci. 
Am. Jour, sa, Borde Serres, Vou. XXVIII, No. 166.—Ocr., 1884. 
