Lenses and Waves

Chapter 3
1655-1672 - 'De Aberratione'
Huygens' practical optics and the aspirations of dioptrical theory
In the decade following Tractatus, Huygens was at home were his
mathematical virtuosity grew to full stature. These are the years of his most
renowned achievements: the invention – in 1656 – improvement and
employment of the pendulum clock and the theory of pendulum that were
the basis of his master piece Horologium Oscillatorium (1673); the discovery in
1655 of a satellite of Saturn and the identification of its ring. Through his
correspondence and publications Huygens increasingly gained recognition
among Europe’s scholars. He traveled abroad, first to Paris in 1655 to meet
the leading French mathematicians, then to Paris and London in 1660-1, and
again in 1663-4, the last time being elected fellow of the Royal Society. There
were squabbles as well, in Italy in particular, over the priority of the
pendulum clock with Florentine sympathizers of the late Galileo and with
the Roman telescope maker Divini over the superiority of his telescopes.
Probably as a result of the clock dispute, he did not obtain a position at the
court of prince Leopold, but in 1666 Huygens realized his learned assets. At
the instigation of Colbert he came to Paris to help organize an ‘académie des
sciences’, thus confirming his status as Europe’s leading mathematician. Life
in Paris, with it competitive milieu, was no unqualified pleasure. Huygens
correspondence shows symptoms of homesickness, he particularly missed
his brother Constantijn, and in 1670 he was was smitten with ‘melancholie’
for the first time. In these years he also experienced the first major setback in
his science: a design for a perfect telescope proved useless. The design was
the outcome of Huygens’ practical activities in telescopy of the late 1650s
and his subsequent theoretical reflections thereupon of the 1660s. These are
the subject of this chapter.
When Huygens’ interest in dioptrics was sparked late 1652, it was both its
theoretical and practical aspects. He immediately began inquiring about the
art of lens making, but he engaged in practical dioptrics only after he put
aside the manuscript of Tractatus. Around 1655, he and his brother
Constantijn acquired the art of lens making and started building telescopes. 1
The practice bore fruit almost immediately. In 1656, Christiaan published a
pamphlet De saturni luna observatio nova on the discovery of a satellite around
Saturn. It was the first new celestial body in the solar system to be
1 Editor’s comment, OC15, 10. See also Anne van Helden, “Lens production”, 70.