Lenses and Waves

1655-1672 - DE ABERRATIONE 89
In his view, white light may also be produced by mixing yellow and blue
alone. By maintaining that there are only two primary colors, Huygens drew
upon a letter published in the 88th issue of Philosophical Transactions (18
November 1672, O.S.) in which Newton responded to comments by Hooke.
Among other things, Hooke had claimed that two primary colors sufficed to
explain the diversity of colors. Hooke’s comments had not been published
and his name was not mentioned in Newton’s reply. Huygens referred to
Hooke’s prism experiments in Micrographia (1665). He suggested an
experiment to verify whether all colors are necessary to produce white light.
Evidently, Huygens had problems with Newton’s claims about the nature of
light. What these problems were exactly, why he would prefer just two
colors, and what he meant by ‘explaining by physics, mechanics’ and ‘some
hypothesis of motion’ is not explained in the letter. In chapter 6 we will be
able to reconstruct, in retrospect, the background to Huygens’ remarks. He
had a reasonably clear idea what mechanistic explanation ought to be, but it
appears that by 1672 he had not yet elaborated in much detail his conception
of the mechanistic nature of light.
Besides raising objections to Newton’s ideas on the nature of light and
colors, Huygens summed up his own treatment of chromatic aberration:
“Apart from that, as regards the effect of the different refractions of rays in telescope
glasses, it is certain that experience does not correspond with what Monsieur Newton
finds, because by considering only the distinct picture that an objective of 12 feet makes
in a dark room, one sees that it is too distinct and too sharp to be able to be produced
by rays that disperse from the 50th part of the aperture so that, as I believe to have
brought to your attention before, the difference of the refrangibility may not always
have the same proportion in the large and small inclinations of the rays on the surfaces
of the glass.” 166
There is no reason to assume that Huygens had not actually performed this
test. 167 We may only wonder why he had not done so in 1665. Then again, the
alleged observations remained qualitative. We may wonder what had
prompted Huygens to consider the issue of chromatic aberration anew.
Assuming that the full import of Newton’s theory had occurred to him as a
result of Pardies’ comments, he may have realized at some time by late 1672
that chromatic aberration was a problem of refraction and thus inherent to
lenses. As Newton emphasized in his reply to Hooke: “And for Dioptrique
Telescopes I told you that the difficulty consisted not in the figure of the
166 OC7, 243-244. “Au reste pour ce qui est de l’effect des differentes refractions des rayons dans les verres
de lunettes, il est certaine que l’experience ne s’accorde pas avec ce que trouve Monsieur Newton, car a
considerer seulement la peinture distincte que fait un objectif de 12 pieds dans une chambre obscure, l’on
voit qu’elle est trop distincte et trop bien terminée pour pouvoir estre produite par des rayons qui
s’escarteroient de la 50 me partie de l’ouverture de sorte que, comme je vous crois avoir mandè desia cy
devant la difference de la refrangibilité ne suit pas peut estre tousjours de la mesme proportion dans les
grandes et petites inclinations des rayons sur les surfaces du verre.”
167 Because he was a ‘devoted water-color painter’, Shapiro is puzzled about Huygens’ assertion that
yellow and blue may produce white, “… because this is contrary to all beliefs about color mixing held in
the seventeenth century.” Shapiro, “Evolving structure”, 223-224. We should bear in mind that Huygens
was also an experienced employer of magic lanterns.