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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![[ ^1^ J clofed, after having been for fome time Ilea- di]y dired:ed to fome bright objed:, a co- loured fpedtrum will become perceptible. The nature of thefe fpedra and the variations in colour to which they are fubjedl, were, fome time fince, made the fubjed: of a very ingenious inveftigation by Dr. Darwin. At prefent we have only to confider the general appearance independent of any particular co- lour. Let the eyes be held fteadily fixed oa one of the above-mentioned lamps for a mi- nute or two, after which, on fuddenly do- ling them, a coloured fpedrum will be feen. If any doubt ihould be entertained whether or not the two eyes are equally afFeded, in this cafe it may be clearly afcertained by looking with one alternately, the other being clofed, at a flieet of white paper, when in either cafe a dark fpot or fpedrum will ap- pear on the face of it, I M^N-](https://iiif.wellcomecollection.org/image/b21175408_0194.jp2/full/800%2C/0/default.jpg)
