Researches in colour vision and the trichromatic theory / by Sir William de W. Abney.
- William de Wiveleslie Abney
- Date:
- 1913
Licence: Public Domain Mark
Credit: Researches in colour vision and the trichromatic theory / by Sir William de W. Abney. Source: Wellcome Collection.
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![more. In this experiment the small particles act like the small particles in the air.1 This investigation of Lord Rayleigh’s, which General Festing and the writer, it is believed, were the first to confirm experimentally, enabled an experiment to be made first of all by Sir George Stokes, by which the debated point as to whether a candle or gas flame was luminous owing to solid particles being rendered incandescent could be settled. If the pencil of light (sunlight by preference) be directed through a candle or gas flame instead of through the turbid medium, a track of the pencil can be seen when examined at right angles to the pencil. When the Nicol’s prism is inserted and turned in one direc¬ tion, the track will be invisible ; if turned in the other direction it will reappear. Fig. 20 gives copies of photo¬ graphs made of the phenomena. Such evidence tends to prove that the particles are solid, though extremely fine. In other words, there does not seem to be much difference in the source of light from an incandescent electric light and that of a candle flame : both appear to be due to incandescent solid carbon. It may, however, be remarked that the illumination given by a fiat gas flame, when it is turned flat side towards an object, will not be quite the same as that given when the flame is turned end on. The reason for this is apparent.] 1 It may be stated that the suspended particles become finer if the water be allowed to rest for a month or two.](https://iiif.wellcomecollection.org/image/b31350574_0081.jp2/full/800%2C/0/default.jpg)
