THE NATURE OF COLOR

THE NATURE OF COLOR

Having thus proved the composition of light, Newton took up an

exhaustive discussion as to colors, which cannot be entered into

at length here. Some of his remarks on the subject of compound

colors, however, may be stated in part. Newton's views are of

particular interest in this connection, since, as we ha 23123n138x ve already

pointed out, the question as to what constituted color could not

be agreed upon by the philosophers. Some held that color was an

integral part of the substance; others maintained that it was

simply a reflection from the surface; and no scientific

explanation had been generally accepted. Newton concludes his

paper as follows:

"I might add more instances of this nature, but I shall conclude

with the general one that the colors of all natural bodies have

no other origin than this, that they are variously qualified to

reflect one sort of light in greater plenty than another. And

this I have experimented in a dark room by illuminating those

bodies with uncompounded light of divers colors. For by that

means any body may be made to appear of any color. They have

there no appropriate color, but ever appear of the color of the

light cast upon them, but yet with this difference, that they are

most brisk and vivid in the light of their own daylight color.

Minium appeareth there of any color indifferently with which 'tis

illustrated, but yet most luminous in red; and so Bise appeareth

indifferently of any color with which 'tis illustrated, but yet

most luminous in blue. And therefore Minium reflecteth rays of

any color, but most copiously those indued with red; and

consequently, when illustrated with daylight--that is, with all

sorts of rays promiscuously blended--those qualified with red

shall abound most in the reflected light, and by their prevalence

cause it to appear of that color. And for the same reason, Bise,

reflecting blue most copiously, shall appear blue by the excess

of those rays in its reflected light; and the like of other

bodies. And that this is the entire and adequate cause of their

colors is manifest, because they have no power to change or alter

the colors of any sort of rays incident apart, but put on all

colors indifferently with which they are enlightened."[2]

This epoch-making paper aroused a storm of opposition. Some of

Newton's opponents criticised his methods, others even doubted

the truth of his experiments. There was one slight mistake in

Newton's belief that all prisms would give a spectrum of exactly

the same length, and it was some time before he corrected this

error. Meanwhile he patiently met and answered the arguments of

his opponents until he began to feel that patience was no longer

a virtue. At one time he even went so far as to declare that,

once he was "free of this business," he would renounce scientific

research forever, at least in a public way. Fortunately for the

world, however, he did not adhere to this determination, but went

on to even greater discoveries--which, it may be added, involved

still greater controversies.

In commenting on Newton's discovery of the composition of light,

Voltaire said: "Sir Isaac Newton has demonstrated to the eye, by

the bare assistance of a prism, that light is a composition of

colored rays, which, being united, form white color. A single ray

is by him divided into seven, which all fall upon a piece of

linen or a sheet of white paper, in their order one above the

other, and at equal distances. The first is red, the second

orange, the third yellow, the fourth green, the fifth blue, the

sixth indigo, the seventh a violet purple. Each of these rays

transmitted afterwards by a hundred other prisms will never

change the color it bears; in like manner as gold, when

completely purged from its dross, will never change afterwards in

the crucible."[3]