Christiaan Huygens (1629–1695) was born at The Hague, the son of the diplomat and poet Constantijn Huygens, and studied law and mathematics at Leiden and Breda. He discovered Saturn's moon Titan in 1655 and explained the planet's ring, invented the pendulum clock and set out its theory in Horologium Oscillatorium (1673), and worked on probability, collision and centrifugal force. From 1666 to 1681 he lived in Paris as a leading member of the new Royal Academy of Sciences, before returning to the Dutch Republic, where he died in 1695.
Christiaan Huygens read the substance of this treatise to the Royal Academy of Sciences in Paris in 1678 and published it in French at Leiden in 1690 as Traité de la lumière, with a short discourse on the cause of gravity. The library text is Silvanus P. Thompson's literal English translation of 1912, complete, with the author's preface, Thompson's note and a table of matters; the many geometrical figures are marked but not reproduced.
