Lenses and Waves

250 CHAPTER 6
strange refraction, his esteem turned into admiration. 126 He valued Huygens’
theory more highly than Pardies’, let alone Ango’s, but he still wanted to hear
Huygens’ opinion on colors and on diffraction. Papin’s response was similar,
but he had doubts whether the hypothesis explaining strange refraction
could be true. 127 From Paris, too, Huygens received appreciation. 128 From
London, Fatio called it a pleasure to read it but also had some comments. 129
Amidst profuse apologies, he confessed he did not quite understand
Huygens’ explanation of strange refraction. How could the wave strike the
eye along rays not perpendicular to it? Huygens’ reply is lost, but Fatio
withdrew his doubts completely and apologized for making objections
without having studied Huygens’ explanation in a satisfactory manner. 130
The correspondence with Fatio is revealing in another regard. The main
part of Fatio’s comments did not concern Traité de la Lumière but Discours de la
Cause de la Pesanteur. In this Fatio was no exception: Principia dominated even
Huygens’ own correspondence. It therefor does not come as a surprise that
the reactions to his own publication were dominated by Discours, his
response to Principia. In this sense, Traité de la Lumière fell between two stools
of gravity. After Huygens had gathered some compliments, it more or less
disappeared from his correspondence. Huygens took no trouble to change
this; apparently he had lost interest again. Early 1690, unbeknown to
Huygens, Traité de la Lumière was discussed at the Royal Society. Hooke raised
objections, mainly pointing out its failure to account for colors. Halley
responded with a paper in which he discussed the virtues of wave theories,
preferring Huygens’ over Hooke’s. 131 Newton, who owned and dog-eared
two copies of Traité de la Lumière, first referred to Huygens in the second
English edition of Opticks in 1717. 132
The subject returned once more in a letter Leibniz wrote on 26 April
1694. Huygens’ theory, he reported, had been expounded by Martin Knorre
at the University of Wittenberg. 133 Along with his own letter, Leibniz sent a
copy of a letter he had received from Fatio, who reported on his and
Newton’s opinions concerning the nature of light and gravity. Fatio and
Newton, Leibniz wrote, still upheld an emission conception of light and
explained different refrangibility with it. Leibniz still had problems with such
126
OC9, 522.
127
OC9, 559-560. It seemed to imply that Iceland crystal was not a homogeneous substance, which
Huygens presupposed in order to explain refraction. Huygens responded that this was a question
concerning the structure of the crystal, on which he had only some speculations: OC10, 177-179.
128
For example from La Hire and Huet: OC10, 5-6; 53.
129
OC9, 381.
130
OC9, 410. On Fatio’s letter, he made a note: “IC is the light ray, but it affects the eye as if coming along
the perpendicular of the wave IK”: OC9, 388. “IC est le rayon de lumiere, mais il agira sur l’oeil comme
venant suivant la perpendiculaire de l’onde IK.” (See Figure 70)
131
Albury, “Halley and Traité de la Lumière”, 449-454. Albury seems to miss the point that Halley was
discussing wave theories only, by claiming that the paper displays his rejection of Newton’s optics.
132
Cohen, “Missing author”, 32.
133 OC10, 601.