This post enabled him to devote himself to the exploration of the Alps, for which he had conceived a great passion ever since an ascent (1761) of the Voirons, near Geneva. In 1775 he made the first ascent of the Buet (3096 m) by the now usual route from the Pierre à Bérard, on which the great flat rock known as the Table au Chantre still preserves his memory. In 1784-1785 he was the first traveller to attempt the ascent of Mont Blanc (not conquered till 1786), but neither then nor later (1788) did he succeed in reaching its summit. On the other hand he reopened (1787) the route over the Col du Géant (3371 m), which had fallen into oblivion, and travelled also among the mountains of the Valais, of the Bernese Oberland.
His writings are composed in a naive, sentimental and rather pompous style, but breathe throughout a most passionate love for the Alps, as wonders of nature, and not as objects of scientific study. His chief works are the Description des glacières de Savoye, 1773 (English translation, Norwich, 1775-1776), the Description des Alpes pennines et rhétiennes (2 vols., 1781), and the Descriptions des cols ou passages des Alpes, (2 vols., 1803), while his Itinéraire de Genève, Lausanne et Chamouni, first published in 1791, went through several editions in his lifetime.