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.

    121/392 page 99
    Without knowing what had been done by the Italian philosopher, our countryman, Dr Robert Hooke, had been diligently occupied with the same subject. In 1672, he communicated his first ob- servations to the Royal Society, and he then spoke of his paper as “ containing the discovery of a new property of light not mentioned by any optical writers before him.” In his paper of 1674, already mentioned, and which is no doubt the one to which he alludes, he has not only described the leading phenomena of the inflexion, or the deflexion of light, as he calls it, but he has distinctly announced the doctrine of interference, which has performed so great a part in the subsequent history of optics.* Such was the state of the subject when Newton directed to it his powers of acute and accurate ob- servation. His attention was turned only to the enlargement of the shadow, and to the three fringes which surrounded it; and he begins his observations by ascribing the discovery of these facts to Grimal- di. After taking exact measures of the diameter of the shadow of a human hair, and of the breadth of the fringes at different distances behind it, he discovered the remarkable fact, that these diame- ters and breadths were not proportional to the dis- tances from the hair at which they were measured. In order to explain these phenomena, Newton sup- posed that the rays which passed by the edge of the * This doctrine is thus announced. 1. That the same rays of light falling upon the same point of an object will turn in- to all sorts of colours by the various inclination of the object. 2. That colours begin to appear when two pulses of light are ae so well and so near together that the sense takes them or one.
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