A reply to Mr. Robin's remarks on the Essay upon distinct and indistinct vision published at the end of Dr. Smith's Complete system of optiks / by James Jurin.
- James Jurin
- Date:
- 1739
Licence: Public Domain Mark
Credit: A reply to Mr. Robin's remarks on the Essay upon distinct and indistinct vision published at the end of Dr. Smith's Complete system of optiks / by James Jurin. Source: Wellcome Collection.
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![[ 5° ] upon the fame fpot G; and almoft all the other fimple rays compoling it, by undergoing a lefs refraction, will fall without the fpot G fpread- ing as far as g. The fpot G will therefore receive from the compound ray CD all its fimple rays of the ex¬ treme red, and from the compound ray CE all its fimple rays of the extreme violet. And after the fame manner you may eafily fee, that the fame fpot will receive the fimple rays of all the intermediate colours from the feveral com¬ pound rays, that fall between D and E, that is, the fimple violet rays of feveral degrees from the feveral compound rays, that lie neareft to E, and the fimple rays of the feveral degrees of in¬ digo, blue, green, yellow and red, from the feveral compound rays, that fall fucceffively upon the cornea from E to D. Now if all the fimple rays we have been fpeaking of, or the greater part of them for number and ftrength, happen to be in their fit of tranfmiffion, at their incidence upon the cor- fiea, and alfo upon both furfaces of the cryftal- line, fo as to fall upon the fpot G, that fpot will be luminous. But if the greater part of thefe fimple rays for number and ftrength happen to be in the fit of reflexion, at the three above-named inciden¬ ces put together ; then the fmaller part of them mult fall upon the fpot G, and confequently that fpot will be comparatively dark in refpeCt of other fpots, which receive a greater proportion of the incident rays tending to them. And although not the greater part, but lefs than half of thefe fimple rays be reflected back » but ftill the fpot G receive a lefs proportion of the](https://iiif.wellcomecollection.org/image/b30780287_0058.jp2/full/800%2C/0/default.jpg)
