The meticulous Airy’s vast correspondence network (many also friends) included Beaufort, FitzRoy, Faraday, Maxwell, Galton, Brunel, Quetelet, Encke, Regnault, Lyell and Owen. He went for long walks with his warm lifetime friend Sedgwick, and visited Southey and Wordsworth in Cumbria, Arago and Laplace in France, and Gauss and Humboldt in Germany. Authoritarian and intolerant of others’ opinions, he had a long and bitter professional argument with Cayley, kept up a running feud with Babbage over everything from telescope design to railway gauges, and effectively terminated funding for his analytical engine.
Herschel, the first to properly map the southern hemisphere stars, also gave the world clear photographic terminology and a number of significant processes. His father William and aunt Caroline were both important influences. He studied alongside Babbage (a close friend and fellow-worker for life), Peacock and Whewell. Darwin, Sedgwick, Lyell and Cameron were all good friends. He showed another friend, Talbot, whom he’d met while both were visiting Fraunhofer, how to fix his pioneering images. Faraday and he, Royal Society colleagues, were warm to one another, while Wollaston helped him find his real métier.
Lacaille made a huge contribution to mapping the southern-hemisphere stars, proposing constellations with suitably ‘enlightenment’ names. Cassini was a mentor, offering the young Lacaille work, lodging and friendship (he went on to improve some of Cassini’s results). Lalande was a close friend as well as colleague, Clairaut a close colleague, Boscovich a friend. Euler, Mayer and La Condamine were all correspondents of Lacaille’s, and Lavoisier one of his students.
An eminent student of Gauss’s, Encke was recommended by Bessel as head of the Berlin observatory, to succeed Bode. He visited Herschel in England, was helped by Humboldt to get an improved observatory built outside Berlin, and told Gauss, Bessel and Olbers of his great discovery of a comet with an unexpectedly short orbital period. Airy, Babbage and Quetelet were correspondents. Encke only grudgingly allowed his assistant (and former student) Galle to search for a previously unknown planet, but as it was Encke’s birthday, he was otherwise engaged; Galle interrupted the party to tell him the great news.
Möbius made significant contributions to the then-young field of topology. Although he was primarily a mathematician, his two most influential teachers were both in astronomy; of them Mollweide’s interests overlapped sympathetically with those of Möbius, while the other — Gauss — was quite simply the greatest mathematician of his time. Grassmann submitted work to Möbius for his doctorate, but Möbius failed to understand its implications; however he later awarded Grassmann a prize (from a field of one).
Zach, an ambitious, well-connected, well-travelled man, established a network of astronomers from the Baltic to the Mediterranean, from England to Poland, leading to the discovery of the Asteroid belt; he also ran significant scientific journals. Olbers, Messier and Gauss (who aged 22 had come to him for instruction) were among the group of astronomers. He taught Humboldt the use of the sextant. He visited Bode in Berlin, Lalande and Laplace in Paris, then Herschel and Banks in London (and rubbed Maskelyne up the wrong way). Pons was his protégé, Śniadecki and Talbot among his widespread correspondents.
Bessel, who left school at 14, was the first to bring acute mathematical accuracy to astronomical measurement; he also discovered the existence of White Dwarfs. Olbers encouraged him to become an astronomer. Gauss met him as an observatory assistant, became a close friend, and later recommended him for an honorary doctorate (to facilitate his appointment to the new Königsberg observatory). He met his admiring correspondent Herschel (with whom he stayed), and Babbage, on a visit to England. Neumann and Jacobi, university colleagues, worked with him to reform the Prussian education system.
The astronomer Olbers (who always kept a ‘day job’ in medicine, and is sometimes known as Heinrich Wilhelm Olbers) and the great mathematician and astronomer Gauss were regular correspondents. Encke told him (and Bessel and Gauss) when he made his momentous discovery of comets with short orbital periods. Struck by the self-taught Bessel’s prodigious talents, Olbers persuaded him to drop the security of his apprenticeship in commerce, and become an astronomer instead.
Lambert’s exceptional range of work is still under-appreciated. Among much else, he developed a pioneering form of non-Euclidean geometry, proved π to be irrational, and was among the first to understand that the Milky Way is a spiral nebula. He met d’Alembert in Paris during a 2-year trip through Europe. Euler invited him to take up a position in Berlin, where Lagrange was also based; as colleagues they extended his work, but Euler and he quarreled, Euler moving on. Bode (with whom he founded an influential astronomical yearbook) and Sulzer were other Berlin colleagues. Kant, a correspondent, greatly admired him.
Méchain and Delambre were together charged with measuring the length of the meridian from Dunkerque via Paris to Barcelona, in order to fix the precise length of the metre. Working separately over a decade, Delambre kept the more secretive Méchain informed of his results, and eventually helped his struggling colleague to complete his task. Delambre taught Comte, minded Thompson, and arranged for publication of Fourier’s work on heat-conduction. He corresponded with Gauss and Maskelyne, enjoyed warm friendly relations with Laplace, attended Ampère’s ill-conceived wedding, and helped him to a job.