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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![[ 4+ ] into Sir Ifaac Newton's Opticks, except only the author of the EJfay upon diflinEl and indiftink Vi- [ion. Hence it is eafy to collect, that if, at any point of the pafiage of a ray of white light, the fimple rays that compofe it, be every one in the middle of the fit of eafy reflexion, the like will not again happen, till the ray fhall have pafs’d through a diftance immenfiy great. For if we fuppofe the compound or white ray to confift of only 38 Ample rays; and the inter¬ val between two fubfequent fits of eafy reflexion in the moft refrangible of thefe rays, be to the like interval in the leaft refrangible, as 63 to 100 ; and the intervals of the intermediate Am¬ ple rays be as the numbers 64, 65, 66-99 then all thefe fimple rays cannot be together in the middle of the fit of eafy reflexion a fecond time, till they have pafs’d through fuch a num¬ ber of intervals of the moft refrangible ray, as would arife from the numbers 64, 65, 66— xoo, continually multiplied into one another. And if inftead of 38, we fuppofe the number of fimple rays, which compofe the ray of white light, to be 380, 3800, 38000, or more, (for we know not where to ltop) we may by this means arrive at fo vaft a number of fits, and confe- quently at fo immenfe a diftance, that in the pafiage of a white ray from the fun, or even from the fixed ftars to the earth, it fhall not twice happen, that all the fimple rays which compofe it, fhall be together in the middle of the fit of eafy reflexion. Hence, if we fuppofe each fimple ray to be reflected back from the cornea of the eye, only when it is in the very middle of the fit of eafy . „ reflexion,](https://iiif.wellcomecollection.org/image/b30780287_0052.jp2/full/800%2C/0/default.jpg)
