By the Rays of Light I understand its least Parts, and those as well Successive in the same Lines, as Contemporary in several Lines.

Opticks by Isaac Newton, is part of the HackerNoon Books Series. Read this book online for free on HackerNoon!

I have now given in Axioms and their Explications the sum of what hath hitherto been treated of in Opticks.

Lights which differ in Colour, differ also in Degrees of Refrangibility.

What that Cause is we shewed above in this tenth Experiment, and need not here repeat it.

To define the Refrangibility of the several sorts of homogeneal Light answering to the several Colours.

Let us now stop the Paper at the Focus G, where the Light appears totally white and circular, and let us consider its whiteness.

I shall in the following Propositions give instances of this in the Phænomena of chiefest note.

By the discovered Properties of Light to explain the Colours made by Prisms.

By the discovered Properties of Light to explain the Colours of the Rain-bow.

For otherwise the Rays which were of one Colour at the Lens might be of another upon the Paper, contrary to what we find.

Superficies therefore which refract most do soonest reflect all the Light which is incident on them, and so must be allowed most strongly reflexive.

The fourth and fifth Iris seem'd of a bluish green within, and red without, but so faintly that it was difficult to discern the Colours.

Nor is it material whether the Hair be encompassed with Air, or with any other pellucid Substance.