Observations on the nature and theory of vision : with an inquiry into the cause of the single appearance of objects seen by both eyes / by John Crisp, F.R.S.
- Crisp, John
- Date:
- MDCCXCVI [1796]
Licence: Public Domain Mark
Credit: Observations on the nature and theory of vision : with an inquiry into the cause of the single appearance of objects seen by both eyes / by John Crisp, F.R.S. Source: Wellcome Collection.
Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.
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![[ ^65 ] In making thefe experiments fome cir- cumftances are to be noticed, a want of at- tention to which, might lead fome to fup- pofe that the experiments did not anfwxr. What is generally underftood by deep- nefs of colour, is not occaiioned by the den- fity of the rays, nor by the intenlity of their ad:ion, but proceeds from their rarity. A few rays of any colour diffufed over a part of the retina would excite the notion of a dark colour; for deepnefs of colour ap- proaches to blacknefs, which is the priva- tion of colour or fenfation. If, therefore, we look through a glafs deeply ftained with any colour with one eye, and iliould either not apply any, or only fome light-coloured glafs to the other eye, it is not to be fup- pofed, that the general appearance wall be that which might be compounded of a deep colour mixed with white or with fome light colour; for the eye which fees through a dark glafs w^ill be affedled only with a weak M 3 fenv](https://iiif.wellcomecollection.org/image/b21175408_0187.jp2/full/800%2C/0/default.jpg)
