In the Summer of 1829, Franz Bopp and August Wilhelm von Schlegel quarreled about Sanskrit sound shifts. They quarreled so badly it ended their correspondence, and they never met again.
They were, at that point, the first two professors of Sanskrit, in Germany and elsewhere. Their friendship dated back from 1814, when Bopp, though twenty years younger, had helped Schlegel with his Sanskrit studies. Bopp had gone to Paris in his early twenties to learn the language, just like August Wilhelm’s younger (and wilder) brother Friedrich had done before. August, at that point already a literary figure of renown and the consort of Madame de Staël, had followed after Napoleon’s exile, and rushed off again when Napoleon returned. Now that both had landed a professorship, the break was probably inexorable: Schlegel was older and famous, but Bopp was evidently the better linguist. Schlegel was no longer in a position to be condescendingly nice and benign.
In his final letter to Bopp, Schlegel writes:
Was Übrigens den Inhalt Ihres Schreibens betrifft, so werden Sie mir verzeihen, wenn ich künftig briefliche Erörterungen über diese Gegenstände vermeide; weil, wie ich sehe, vertrauliche Mittheilungen Ihnen unwillkommen sind, sobald eine Divergenz der Meynungen hervortritt. Was man durch den Druck dem Publikum übergeben hat, fällt ohnehin mit unsrer eignen Zustimmung der öffentlichen wissenschaftlichen Prüfung anheim.In the same letter, the appellation shifts from “Hochgeehrter Herr und Freund” to a frosty “Ew. Wohlgeboren”. Apparently Schlegel did not realize how arrogant his previous letter had been, in which he had criticized Bopp’s Sanskrit grammar. (Heinrich Heine describes him as almost ridiculously vain.) Now it is very sad that they quarreled and stopped being friends, but the reasons why are interesting.