Jaucourt wrote about 18,000 articles (a quarter of the total) for Diderot and D’Alembert’s Encyclopédie in the 1750s and 1760s, at the rate of 7 or 8 a day.
The Chevalier de Jaucourt (1704-1779), as his title shows, was the younger son of a noble house. He studied at Geneva, Cambridge, and Leyden, and published in 1734 a useful account of the life and writings of Leibnitz. When the Encyclopædia was projected, his services were at once secured, and he became its slave from the beginning of A to the end of Z. He wrote articles in his own special subjects of natural history and physical science, but he was always ready to lend his help in other departments, in writing, rewriting, reading, correcting, and all those other humbler necessities of editorship of which the inconsiderate reader knows little and thinks less. Jaucourt revelled in this drudgery. God made him for grinding articles, said Diderot. For six or seven years, he wrote one day, Jaucourt has been in the middle of half a dozen secretaries, reading, dictating, slaving, for thirteen or fourteen hours a day, and he is not tired of it even now. When he was told that the work must positively be brought to an end, his countenance fell, and the prospect of release from such happy bondage filled his heart with desolation. “If,” says Diderot in the preface to the eighth volume (1765), “we have raised a shout of joy like the sailor when he espies land after a sombre night that has kept him midway between sky and flood, it is to M. de Jaucourt that we are indebted for it. What has he not done for us, especially in these latter times? With what constancy has he not refused all the solicitations, whether of friendship or of authority, that sought to take him away from us? Never has sacrifice of repose, of health, of interest been more absolute and more entire.” These modest and unwearying helpers in good works ought not to be wholly forgotten, in a commemoration of more far-shining names.
John Morley, Diderot and the Encyclopedists
Though he was financially independent, Jaucourt did all the work gratis to the point that he sold one of his houses in order to pay for the secretaries. I doubt it bothered him too much, since there doesn’t seem to be much record of him doing anything with his life other than reading and researching.