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.

Jurin, James, 1684-1750.

Date:: 1739

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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$[ '3 ] v“ The r rays of light in their motion through “ the air, or any other tranfparent medium, “ are not alike difpofed in every part of their “ paffage in regard to reflection and refraCtion \ “ infomuch that in fome places, if they meet “ with another tranfparent fubftance, they (hall “ enter it freely, fuffering only a refraCtion at “ the furface upon its tranfmiilion through into “ the tranfparent fubftance, but in other places “ the fame ray fhall be difpoled to be reflected “ back from any fuch fubftance in its way.” A Reader lefs converfant in their works might pofilbly take this for nonfenfe. Such a one, when he meets withs this darkfpot, the1 fame ray, thefe u alternate difpofitions, of which he has feen no mention before, would be apt to turn back in hopes to find fome previous account of the fpot, the ray, and the alternate difpofitions. But that is not Mr. Robins or his Matter’s way of writing. Fefinal, & in medias res Nonfecus ac notas auditorem raft. But let us pafs over thefe beauties of ftyle, and come to fomething more material. It is laid, x “ Sir Jfaac Newton divides thefe “ intervals (between the fit of eafy tranfmiffion “ and the next fit of eafy reflexion) into two “ equal parts, as here y CD is divided atg, and “ D E at h ; and confiders the whole fit of re- 4‘ flexion to be extended between g and h, but “ ftrongeft at D, ^ In another place we are tord, Sir Ijaac “ Newton in the fame ray makes the fit of re- “ flexion v Remarks, p. 98. K Ibid. p. 9^* hfi* 1 7* 99- 3* u Ibid. lin. 5, x Ibid. p. 99. y See Mr. Roblnit figure, p, 90. f Remarks, p. ill.$