Lenses and Waves

1690 - TRAITÉ DE LA LUMIÈRE 253
Some ambivalence resounds in the judgements of men like Laplace and
Lagrange. Huygens brought the science of motion to a new level, but did not
develop this into a new science like Newton. 144
By the end of the eighteenth century Huygens’ investigation of strange
refraction underwent a more positive valuation. However, his natural
philosophical ideas met with doubts. In his Exposition du système du Monde of
1796 Laplace observed:
“ … [the insufficient explanation of spheroidal waves and polarization] combined with
the difficulties the theory of luminous waves presents is the cause why Newton and the
majority of geometers who have followed him failed to appreciate with justice the law
Huygens attached to it.” 145
Malus praised Huygens for finding an accurate law of strange refraction, but
lamented his troublesome ‘system of undulations’:
“That law, considered in itself and cleared of the explanation to which Huygens had
attached it is one of the finest discoveries of that celebrated geometer.” 146
He did not realize that this troublesome system was essential to the discovery
of the law and was inherently connected to it. 147 He did not recognize the
new way of studying light mathematically that was being pursued in Traité de
la Lumière. His physical optics still had to be rediscovered. Nineteenthcentury
students like Fresnel developed a Huygens-like way of doing optics
in which microphysical hypotheses were the starting point of the
investigation – a way Huygens himself had barely recognized as a kind of
‘Optique’ that went beyond geometrical optics.
144 Bachelard, “Influence”, 244-247.
145 Laplace, Oeuvres Complètes 6, 353-354. “… joint aux difficultés que présente la théorie des ondes
lumineuses est la cause pour laquelle Newton et la plupart des géomètres qui l’ont suivi n’ont pas
justement apprécié la loi qu’Huygens y avait attachée.”
146 Malus, Theorie de la double réfraction…, 289-290. “Cette loi, considérée en elle-même et débarrassée de
l’explication à laquelle Huygens l’avait attachée, est une des plus belles découvertes de ce célèbre
géomètre.”
147 The eighteenth-century development of mechanics, in which mathematical science and natural
philosophy tacitly drifted apart, is illuminating in this regard. See Boudri, Het mechanische van de mechanica, in
particular 257-265.