French translation of the first two volumes of his _Essay on Man_. In this year he visited Edinburgh, and on the recommendation of certain Edinburgh physicians was made an M. D. of St Andrews. On his return to London he published an _Enquiry into the Nature, Cause, and Cure of a Singular Disease of the Eyes_, with a dedication to the Royal Society. In the same year there appeared the third volume of the French edition of the _Essay on Man_, which reached Ferney, and exasperated Voltaire, by its onslaught on Helvetius, into a sharp attack which only made the young author more conspicuous. His fame as a clever doctor was now great, and on the 24th of June 1777, the comte d'Artois, afterwards Charles X. of France, made him by brevet physician to his guards with 2000 livres a year and allowances. Marat was soon in great request as a court doctor among the aristocracy; and even Brissot, in his _Mémoires_, admits his influence in the scientific world of Paris. The next years were much occupied with scientific work, especially the study of heat, light and electricity, on which he presented memoirs to the Académie des Sciences, but the academicians were horrified at his temerity in differing from Newton, and, though acknowledging his industry, would not receive him among them. His experiments greatly interested Benjamin Franklin, who used to visit him and Goethe always regarded his rejection by the academy as a glaring instance of scientific despotism. In 1780 he had published at Neuchâtel a _Plan de législation criminelle_, founded on the principles of Beccaria. In April 1786 he resigned his court appointment. The results of his leisure were in 1787 a new translation of Newton's _Optics_, and in 1788 his _Mémoires académiques, ou nouvelles découvertes sur la lumière_.