The time of perception as a measure of differences in sensations / by Vivian Allen Charles Henmon.

  • Henmon, Vivian Allen Charles (V. A. C.), 1877-
Date:
1906
Catalogue details

Licence: In copyright

Credit: The time of perception as a measure of differences in sensations / by Vivian Allen Charles Henmon. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    Konig and DietericT made the most complete investigation of the sensitivity of the normal eye to differences in wave-lengths. A more detailed account of this research will be given because of its bearing upon this study and the possibility of a comparison of results. For their purposes they employed the Helmholtz spectrophotometer, con- sisting of an equilateral flint-glass prism about which are arranged three collimators. Two of the collimators could be rotated about the axis of the apparatus, the amount of rotation being indicated on finely graduated scales. The other, which served as a telescope for ob- servation, was stationary and directed toward one edge of the prism. It was so adjusted that the edge of the prism formed the vertical diameter of the objective, and an observer looking through the dia- phragm saw the two prismatic surfaces side by side. The diaphragm situated in the focal plane of the telescope contained a movable slit parallel to the slits of the collimators through which light from gas- lamps with Argand burners was allowed to enter. Light passing through the collimators formed in the plane of the diaphragm, the ocular in the telescope being removed, two spectra, one on each of the surfaces of the prism. By proper adjustment of the width of the diaphragm slit, nearly monochromatic light was visible to the observer. An alteration of position of one of the collimators brought about a change in its color, the amount of the alteration being registered on the scales. The determinations of the measurements on these scales were made by using lithium, thallium, natrium, etc. The method of average error was followed in the experiments. An experiment consisted in adjusting one collimator with reference to the other until the colored fields, which appeared side by side in the telescope, seemed to be alike in color. Twenty-two places in the spectrum, equidistant from each other and ranging from 430/z/z to 640/z/x, were investigated. Beyond these limits differences in bright- ness only, and not differences in color-tone, could be perceived. Fifty experiments were made at each place by each of the two subjects, K and D, with two intensities of illumination. For the region from 640fipi to 520fiji, the average errors were the same for the two in- tensities and hence are grouped together. From 520/t/t to 430/i,«, the different intensities caused divergences in the course of the curve, as will be pointed out below. The curve of sensitivity beginning with Q40jj.fi fell gradually to the line D, where the first maximum was obtained. This maximum point appeared for K at 590//// and for D at 570////. There was a slight rise again in the greens and then a fall at F, where the greatest sensitivity was found. Mandelstamm, Dobrowolsky and Peirce had 1 A. Konig and C. Dieterici, Wiedemann's Anvalen, 22: 579-589, 1884, and A. Konig, Abhandlungen zur physiologischen Optik, Leipzig, pp. 23-33, 1903.