Astronomical and Physical Observations Made in the Realm of Peru


Jorge Juan y Santacilia (1713‒73) was born in Alicante, Valencia. A humanist, naval engineer, and scientist, he was one of the most prominent scholars of the Spanish Enlightenment. A versatile man who promoted Enlightenment ideas in Spain, he enjoyed prestige throughout Europe, where he was known as “the learned Spaniard.”  His observations led to improvements in the metric system and helped to determine the exact shape of the Earth, proving that it is not perfectly round. He also played a decisive role in the reform of shipyards during the rule of King Ferdinand VI and in the improvement of the academic education of midshipmen. He was the author of a most important work on the construction of ships, Examen marítimo (Maritime exam), published in 1771, a guide that was translated into all European languages. He measured the longitude of the meridian of the Earth, thus demonstrating that the planet is flattened at the poles. In 1735, together with Antonio de Ulloa, he was selected to join a Franco-Spanish expedition to measure the Equator and determine the degree of flattening at the poles and to perfect a theory on the shape of the Earth. He returned to Spain in 1745. In 1748 he published the book presented here, Observaciones astronómicas y físicas, hechas de orden de S.M. en los reinos del Perú (Physical and astronomical observations made by order of H.M. [His Majesty] in the Kingdoms of Peru), as well as Relación histórica del viaje a la América meridional (Historical account of the trip to South America). In 1751 he was appointed captain of the Midshipmen Company of Cadiz, where the most advanced naval education of the time was provided. Among other initiatives, he founded the Astronomical Observatory of Cadiz and created the Asamblea Amistosa Literaria, predecessor to the Academy of Sciences. During his final years he served as a diplomat in Morocco and as a consultant on various matters to the Ministry of State and the Council of Castile in Madrid.

Last updated: September 5, 2017