Scholar of international renown

In Paris, Huygens drew up the research agenda of the Académie. He himself made important contributions, especially in the area of mechanics, and several of his discoveries were discussed in the meetings of the Académie. Among his most important works of this period was the Horologium Oscillatorium of 1673, in which he derived the laws of the pendulum and proposed an improved pendulum clock. Huygens was one of the central figures in Parisian scientific circles and became an international authority.

He worked hard, and apparently felt at ease in this situation, but he began to experience health problems. In 1669 he became so ill that people were worried that he might die. In order to recuperate, he returned to his family in The Hague, where he remained from September 1670 until June 1671. When, in 1681, illness threatened his life for a second time, he again returned to The Hague.

When the French King declared war on the United Dutch Provinces in 1672, there were no repercussions for Huygens’s position. His family occupied important positions in the administration of the new Dutch stadtholder, Prince William III of Orange, who quickly emerged as Louis XIV’s arch enemy. But Christiaan remained at his post in Paris. He even dedicated the Horologium Oscillatorium to the French King.

In the course of time, the climate in France became less tolerant, however. The freedom of religion of the Protestants were progressively restricted, a trend that was to culminate in the revocation of the Edict of Nantes in 1685, and foreigners of Protestant lands increasingly became the subjects of suspicion. On the advice of friends familiar with the conditions in Paris, Huygens, who had been in The Hague because of illness since 1681, finally decided not to return to Paris.