By Johan C.-E. Stén
The Finnish mathematician and astronomer Anders Johan Lexell (1740–1784) was once a long-time shut collaborator in addition to the educational successor of Leonhard Euler on the Imperial Academy of Sciences in Saint Petersburg. Lexell was once at first invited via Euler from his local city of Abo (Turku) in Finland to Saint Petersburg to aid within the mathematical processing of the astronomical info of the approaching transit of Venus of 1769. many years later he turned a typical member of the Academy. this is often the first-ever full-length biography dedicated to Lexell and his prolific clinical output. His wealthy correspondence specifically from his grand travel to Germany, France and England finds him as a lucid observer of the highbrow panorama of enlightened Europe. within the skies, a comet, a minor planet and a crater at the Moon named after Lexell additionally perpetuate his memory.
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Practical matters were dealt with in the Academic Consistory, consisting of the board of professors, presided over by the Rector. The premises of the university were unpretentious, and the lecture rooms of the Academy remained small and incommodious for the whole of the eighteenth century . 7 Wednesdays and Saturdays were reserved for thesis defences. As there generally was no heating in the classrooms, the students had to endure the lectures in extreme conditions during 6 The complimentary poem written by Fredrik Pryss (1741–1767) suggests, however, that Lexell was considered the most zealous and talented student of his class (Lexell assiduos inter celebrandus alumnos, qui claret studiis ingenioque suo).
E65). On the other hand, the expression they have in common is typical of works in integral calculus of the time. 30 2 Humble Beginnings Philosophical Faculty of Uppsala University for 19 February 1763 state that Lexell, during the absence of Professor Meldercreutz,20 had quickly applied for permission to preside the dissertation of the thesis as a recommendation for “some position in Stockholm” and, consequently, a student by the name of Erik Östling was assigned to defend the thesis (pro exercitio).
E. quadrants fixed to a wall, could also serve as passage instruments (the sextant is a better known portable version of the instrument). Telescopes used for the closer study of the celestial objects were of two kinds (and many varieties): refractors, where the light from a star is collected by a lens, and reflectors, where the light is collected by a concave mirror. At the beginning of the eighteenth century, refractor telescopes suffered from achromatic error, that is, the blurring of the image due to the differing refractive indices for light of different colours.