Astronomy in Leiden till De Sitter’s Arrival

Abstract

De Sitter called Jacob Gool in his brochure of 1933, on the occasion of 300 years of Leiden Observatory, the founding father of the Observatory. Jacob Gool, or latinized Golius (1596–1667) studied mathematics in Leiden with Willebrord Snel van Royen, latinized Snellius (1580–1626), who was professor of mathematics at Leiden University and famous for his law on the refraction of light rays. In order to study the works of the Greek mathematician Apollonius in Arabic translations, Gool studied Arabic and became a prominent Arabist as well. In the morning he lectured on mathematics, physics or astronomy and in the afternoon on Arabic language or literature. Descartes became one of his students in mathematics. In 1632 Gool persuaded the University of Leiden to buy the so-called Quadrant of Willem Blaeu (1571–1638; cartographer) from Snellius and to pay for a small wooden structure on the roof of the Academy building to be used as a modest Observatory.