isaac newton book Page 26-27

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and X LJT area unit 2 Rays, the firſt of that

comes from the lower a part of the Sun to the

isaac newton book

higher a part of the Image, and is refracted within the within the K and H, and therefore the latter comes from the upper {part of|a a part of} the Sun to the lower part of the Image, and is refracted at L and J. Since the Refractions on each each the Priſm area unit e- qual to at least one another, that's the Refraction at K up to the Refraction at J, and therefore the Refra- etion at L up to the Refraction at H, ſo that the Refractions of the incident Rays at K and L taken along area unit up to the Refractions of the emerging Rays at H and J taken together: it follows by adding equal things to equal things, that the Refractions at K and H taken along, area unit up to the Refractions at J and L taken along, and so the 2 Rays being e- qually refracted have the ſame Inclination to at least one another once Refraction that they'd before, that's the Inclination of [*fr1] a Degree

anſwering to the Sun's Diameter. For ſo nice

was the Inclination of the Rays to at least one another before Refraction. So then, the length of the Image Pt would by the principles of Vulgar Op- ticks fubtend AN Angle of [*fr1] a Degree at the Priſm, and by conſequence be up to the breadth o w; and so the Image would be spherical. therefore it'd be were the 2 Rays XLJT and YKHP, and every one and every one that type the Image P W T v, alike refrangible. and so and so expertise it's found that the Image isn't spherical however regarding 5 times longer than broad, the Rays that go- ing to the higher finish P of the Image fuffer the

SA

greateſt

[ 27 ]

greateſt Refraction, muſt be a lot of refrangible

than thoſe that visit the lower finish T, un-

leſs the difference of Refraction be caſual.

This Image or Spectrum P T was colored,

being red at its leaſt refracted finish T, and vio-

let at its moſt refracted finish.P, and yellow

green and blue within the intermediate areas.

Which agrees with the firſt Propoſition, that

Lights that dissent in color do alſo dissent in

Refrangibility. The length of the image within the

foregoing Experiments I meaſured from the

fainteſt and outmoſt red at one finish, to the

fainteft and outmoſt blue at the opposite finish, ex-

cepting solely a touch shadow, whoſe breadth

ſcarce exceeded 1 / 4 of an in., as was

faid above. Exper. 4. within the Sun's beam that was pro- pagated into the area through the opening within the Window-fhut, at the diſtance of ſome Feet from the opening, I command the Priſm in fuch a po- fture that its Axis may well be perpendicular thereto beam. Then I looked through the Priſm upon the opening, and turning the Prifm to and fro concerning its Axis to form the Image of the opening the opening deſcend, once between its 2 contrary Motions it ſeemed Stationary, I ſtopp'd the Priſm that the Refractions of each fides of the refracting Angle may well be adequate to one another, as within the former Experiment. during this state of affairs of the Priſm viewing through it the faid hole, I obſerved the length of its re- fracted Image to be again and again larger than its breadth, which which refracted half therefrom appeared violet, the leaſt refracted red,

the

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