Lenses and Waves

1655-1672 - DE ABERRATIONE 87
Newton realized that Huygens did not grasp the full import of his theory.
Reacting to Huygens’ first comment on his theory, he had written Oldenburg
on 13 April (O.S.):
“Monsieur Hugenius has very well observed the confusion of refractions neare the
edges of a Lens where its two superficies are inclined much like the planes of a Prism
whose refractions are in like manner confused. But it is not from ye inclination of those
superficies so much as from ye heterogeneity of light that that confusion is caused.” 155
This remark was not,
however, communicated
to Huygens. On July 8
(O.S.), Newton replied to
Huygens’ second
comment in a letter
Oldenburg forwarded to
Huygens on 28 July. 156 He acknowledged that the presentation of his theory
might have been obscure for reasons of brevity. Newton also realized that
Huygens had misread his discussion of chromatic aberration. “But I see
not,” he wrote, “why the Aberration of a Telescope should be more than
about 1/50 of ye Glasses aperture”. He included a drawing of the way he
had calculated the proportion (Figure 35):
“Now, since by my principles y e difference of Refraction of y e most difforme rayes is
about y e 24 th or 25 th part of their whole refraction, y e Angle GDH will be about a 25 th
part of y e angle MDH, and consequently the subtense GH (which is y e diameter of y e least
space, in to which y e refracted rays converge) will be about a 25 th of y e subtense MH,
and therefore a 49 th part of the whole line MN, y e diameter of y e Lens; or, in round
numbers, about a fiftieth part, as I asserted.” 157
The same letter was accompanied by a copy of the 84th issue of Philosophical
Transactions (17 June, O.S.). It contained a letter in which Pardies criticized
Newton’s theory and a reply by the latter. Two weeks later, Oldenburg sent
Huygens the next issue of Philosophical Transactions (15 July, O.S.) containing
further correspondence of Pardies and Newton on the matter. 158 Pardies, a
Jesuit priest and a Parisian acquaintance of Huygens, also criticized Newton’s
claims, but in a more searching manner and with a different line of approach.
He questioned the core of Newton’s theory – different refrangibility – and
raised several objections to his experiments and his interpretations thereof.
For example, he initially doubted whether the oblong spectrum could not be
explained by the accepted rules of refraction. 159 He also questioned the very
idea of different refrangibility, which in his view depended upon a
corpuscular conception of light. In his view, colors could also be caused by a
‘diffusion’ of light, for example by a slight spreading of the waves he
155
Newton, Correspondence I, 137.
156
Newton, Correspondence I, 212-213; OC7, 207-208.
157
OC7, 207-208.
158
OC7, 215.
159
Newton, Correspondence 1, 131-132.
Figure 35 Newton’s determination of chromatic aberration.