Joseph-Nicolas Delisle (; 4 April 1688 – 11 September 1768) was a French astronomer and cartographer. Life Joseph was born in Paris, one of the 11 sons of Claude Delisle (1644–1720). Like many of his brothers, among them Guillaume Delisle, he initially followed classical studies. Soon however, he moved to astronomy under the supervision of Joseph Lieutaud and Jacques Cassini. In 1714 he entered the French Academy of Sciences as pupil of Giacomo Filippo Maraldi. In the next year he discovered Arago spot a century before Arago. Though he was a good scientist and member of a wealthy family he did not have much money. In 1712, he set up an observatory at the Luxembourg Palace and after three years moved to the Hotel de Taranne. From 1719 to 1722 he was employed at the Royal observatory, before returning to his observatory at the Luxembourg Palace. In 1724 he met Edmond Halley in London and, among other things, discussed transits of Venus. His life changed radically in 1725 when he was called by the Russian czar Peter the Great to Saint Petersburg to create and run the school of astronomy. He arrived there only in 1726, after the death of the czar. He became quite rich and famous, to such an extent that when he returned to Paris in 1747, he built a new observatory in the palace of Cluny, later made famous by Charles Messier. Also he received the title of Astronomer from the Academy. In Russia he prepared the map of the known North Pacific that was used by Vitus Bering. He was elected a Fellow of the Royal Society in 1725 and a foreign member of the Royal Swedish Academy of Sciences in 1749. In 1760 he proposed that the international scientific community co-ordinate observations of the 1761 Transit of Venus to determine the absolute distance of the Earth from the Sun. He developed a map showing where on Earth this transit would be visible and thus where various observing stations should be located. Actual implementation of these observational efforts were hindered by the Seven Years' War. In 1763 he retired to the Abbey of St Genevieve, dying in Paris sometime in 1768. Expedition to Siberia In 1740, Delisle undertook an expedition to Siberia with the object of observing from Beryozovo the transit of Mercury across the sun. An account of the expedition is given in Volume