Copy 1

The life of Sir Isaac Newton / By David Brewster.

  • David Brewster
Date:
1831
Catalogue details

Licence: Public Domain Mark

Credit: The life of Sir Isaac Newton / By David Brewster. Source: Wellcome Collection.

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    hair are deflected or turned aside from it, as if by a repulsive force, the nearest rays suffering the great- est, and those more remote a less, degree of deflex- , Fig. 10. | bs oe Tag (| ) Thus, if X, Fig. 10, represents a section of the hair, and AB, CD, EF, GH, &c. rays passing at dif- ferent distances from X, the ray AB will be more deflected than CD, and will cross it at m, the ray CD, will for the same reason cross EF at n, and EF will cross GH at 0. Hence the curve, or caustic formed by the intersections m, n, 0, &c. will be con- vex outward, its curvature diminishing as it recedes from the vertex. As none of the passing light can possibly enter within this curve, it will form the boundary of the shadow of X. The explanation given by Sir Isaac of the co- loured fringes is less precise, and can be inferred only from the two following queries. 1. “ Do not the rays which differ in refrangibi- lity differ also in flexibility, and are they not by
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