Réaumur was a scientist of unbounded curiosity, many of whose investigations and discoveries show a mind ahead of its time. He was taught by Varignon, dined regularly with Buffon, put a geometric problem concerning honeycombs to his friend König, produced the first systematic study of insect life, and prompted Jussieu to show that corals were animals not plants. He taught Bonnet, Trembley, Spallanzani and Guettard, researched electricity with his younger colleague Nollet, and was assisted by Pitot. Musschenbroek wrote to him about his Leyden-jar experiments; Haller and Morgagni also corresponded.
Lomonosov was one of Russia’s greatest scientists, though in his time was mainly known as a writer: a true polymath, he published work in physics, chemistry, geology, astronomy, classics, language and history, largely working alone. Wolff influentially taught him in Germany. He became Euler’s assistant and later his close colleague in St Petersburg; they corresponded until Lomonosov’s death. He stood as guarantor for his friend and colleague Gmelin, who defaulted (Euler intervened, Gmelin paid him back). He warmly supported Müller’s explorations in Siberia, but (both were hot-headed) took violently against his theory of a Norse origin for the Russian nation.
Maupertuis was taught by Bernoulli, who encouraged his development of Newton’s theories; König was a fellow-student, though a famous and bitter mathematical quarrel marked their last years. Marivaux was a friend as a young man in Paris. Maupertuis was Châtelet’s geometry tutor and lover, and also taught Buffon. Clairaut accompanied him on a year-long expedition to Lapland (they met Celsius en route), though the friendship eventually deteriorated. His great friend Euler wrote to him for two decades, and deputised for him in Berlin. Voltaire had been a good friend, but mocked his ideas and his relations with Lapp women.
Pictet was a travelling-companion, and student, of Saussure, later succeeding him in his university chair. Jefferson, Humboldt (also a friend), Ampère, Ørsted, Berzelius, Berthollet, Chladni, Fourcroy, Lalande, Volta and Zach were among his extensive correspondents. He took Owen on a trip to France and Switzerland (picking up Pictet’s friend Cuvier en route), so Owen could meet with influential continental thinkers. Davy, visiting Geneva with his assistant Faraday, investigated solar radiation with Pictet. De la Rive was one of his colleagues on a significant scientific journal of the time, ‘Bibliothèque Britannique.’ Bonnet complemented him on his mode of interrogation of nature.
Goethe met Herder as a student, and visited Lavater in Switzerland ( a great correspondent, he helped Lavater with his magnum opus on physiognomy). Hummel like him was attached to the Weimar court, where Schopenhauer’s mother had a salon. Schiller approached him in admiration: they became friends and colleagues for life. Carlyle, Schelling, Schlegel, Byron, Hegel and Fichte were among intellectuals drawn across Europe to visit him (Manzoni and he just corresponded). Beethoven set several of his poems to music (though they did not get on personally), and the young Mendelssohn charmed the old man with his playing.
Monge was something of a protégé of Bossut’s. Condorcet and d’Alembert encouraged him to submit research papers to the Académie des Sciences. He taught Malus and Hachette as well as Fourier, who described him as very learned, and having a loud voice. Berthollet, an intimate friend, accompanied him on Bonaparte’s expedition to Egypte, where with Malus and Fourier he became a member of the Institut d’Égypte. Monge collaborated with Lavoisier, and visited his friend Lagrange when the latter was dying.