Christiaan Huygens (1629-1695) was a Dutch mathematician, astronomer and physicist perhaps most renowned for his study of the planet Saturn, the analysis of its rings, and using his own telescopic lens to discover Saturn’s moon Titan in 1655 (O’Connor and Robertson, 1997). Huygens enjoyed an upbringing which provided him with an enviable access to the world of mathematics and science, largely thanks to his father Constantin, himself a natural philosopher (physicist). Christiaan corresponded regularly with two famous mathematicians René Descartes (1596-1650), and Marin Mersenne (1588-1648), as well as receiving private tutoring in his home until he was 16.

Christaan Huygens, *Opera varia* (Leiden, 1724), frontispiece portrait.

Huygens embraced the opportunities afforded to him by these connections and became one of the biggest names of his era in both mathematics and science. Worth obviously had an appreciation for Huygen’s genius as his collection includes nine works by Huygens. The *Opera varia*, published in 1724 is a Latin text containing two volumes which reflect Huygen’s lifework very well. Volume one contains *Opera mechanica* and *Opera geometrica* while volume two contains *Opera astronomica* and *Opera miscellanea.*

While mechanics, geometry and astronomy are subjects with which Huygens will be perpetually connected, the mysteriousness of the last title entices one to investigate its contents. It is testament to Huygens’ broad interest and ability in mathematics that this section of *Opera Varia* includes a body of remarkable work on probability and combinatorics. In fact, he is credited with introducing the concept of mathematical expectation in probability (Epstein, 2009)

Christaan Huygens, *Opera varia* (Leiden, 1724), p. 357.

**Sources**

Epstein, Richard A. *The Theory of Gambling and Statistical Logic* (Academic Press: Cambridge, 2009), p 3.

O’Connor, J.J. and E.F. Robertson, Christiaan Huygens, *MacTutor History of Mathematics* (University of St Andrews, 1997).

**Text:** Fionnán Howard