Lenses and Waves

88 CHAPTER 3
supposed light to consist of. 160 In his two successive replies, Newton clarified
his experiments and his claims. He fully convinced Pardies of his claims and
the father ended the discussion by saying that he was ‘very satisfied’. 161
One expects that by now, late July, it must have dawned upon Huygens
what Newton’s new theory was about. Still, the letter he sent Oldenburg on
27 September does not give the impression that he really grasped the essence
of different refrangibility. 162 He regarded Newton’s replies as a further
confirmation of the theory, but added that things could still be otherwise. It
had, however, dawned upon him that Newton had also something to say
about the nature of light, to wit the compound nature of white light. To this
he raised objections of a different kind:
“Besides, if it were true that the rays of light were, from their origin, some red, some
blue etc., there would still remain the great difficulty of explaining by the physics,
mechanics wherein this diversity of colors consists.” 163
The remark was clearly inspired by the objections Pardies had made. It does
not give the impression that Huygens had given the matter any further
thought. Let it be noted that this was the first moment Huygens raised
objections of a mechanistic nature against Newton, after their discussion had
progressed in several letters, and that the objections are not brought out
strongly. He still did not refer to the notion of different refrangibility. As a
conclusion he admitted his misreading of Newton’s discussion of chromatic
aberration.
Huygens’ next letter to Oldenburg, four months later on 14 January 1673,
displayed a drastic change in his attitude towards Newton’s theory. Not only
did he show to have considered the claims about the nature of white light
and colors, he also subjected them to a serious critique. 164 In addition, the
tone of his comments became sharper. In his view Newton unnecessarily
complicated matters:
“I also do not see why Monsieur Newton does not content himself with the two colors
yellow and blue, because it will be much easier to find some hypothesis by motion that
explains these two differences, than for so many diversities as there are of other colors.
And until he has found this hypothesis he will not have taught us wherein the nature
and diversity of colors consists but only this accident (which certainly is very
considerable) of their different refrangibility.” 165
160
Newton, Correspondence 1, 157.
161
Newton, Correspondence 1, 205. “Je suis tres satisfait de la derniere réponse que M. Newton a bien voulu
faire à mes instances.”
162
Sabra, Theories of Light, 270.
163
OC7, 228-229. “De plus quand il seroyt vray que les rayons de lumiere, des leur origine, fussent les uns
rouges, les autres bleus &c. il resteroit encor la grande difficultè d’expliquer par la physique, mechanique
en quoy consiste cette diversitè de couleurs.”
164
OC7, 242-244.
165
OC7, 243. “Je ne vois pas aussi pourquoy Monsieur Newton ne se contente pas des 2 couleurs jaune et
bleu, car il sera bien plus aisè de trouver quelque hypothese par le mouvement qui explique ces deux
differences que non pas pour tant de diversitez qu’il y a d’autres couleurs. Et jusqu’a ce qu’il ait trouvè
cette hypothese il ne nous aura pas appris en quoy consiste la nature et difference des couleurs mais
seulement cet accident (qui assurement est fort considerable) de leur differente refrangibilitè.”