Colour vision : being the Tyndall lectures delivered in 1894 at the Royal Institute / by Capt. W. de W. Abney; with coloured plate and numerous diagrams.

  • Abney, William de Wiveleslie, Sir, 1843-1920.
Date:
[1895?]
Catalogue details

Licence: Public Domain Mark

Credit: Colour vision : being the Tyndall lectures delivered in 1894 at the Royal Institute / by Capt. W. de W. Abney; with coloured plate and numerous diagrams. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    and passing through the centre, and another rod attached to it at the centre of the sjjhere of exactly the length of the radius. If this last arm be opened to make an angle of 5° with the fixed rod, and be twisted round like the leg of a compass against the bowl, it will make a circle, the projection of which will give the innermost circle of the diagram ; if opened to 10° it will give the next circle, and so on for every subsequent 10°. The lines passing through the centre are 30° from one another, the line stretching from 360° to 180° Ijeing a line supposed to be vertical. By means of an instrument called the perimeter, the field of vision for each eye can be measured. With its aid any small object can be made to fall on any part of the retina by directing the axis of the eye to a fixed point and moving the oljject along one of the diameters. Suppose w^e wish to ascertain the field for a white object, a small white disc is moved, say, along the horizontal line, and the angles at which the retina just no longer sees it are noted. This gives two points in the field, and they are plotted on the cliart—in Fig. 3 one touches the outside circle, and the other is at an angle of about 65°. The field of vision is next tested along another line, say 300° to 120°, and other points noted and marked on the chart. When