(1) Autograph letter to his brother, Guillaume Antoine Deluc. (2) Autograph manuscript (fragment from a larger work) by G.-A. Deluc

Geneva, 1781. Deluc, Jean André (1727-1817). (1) Autograph letter to his brother, Guillaume Antoine Deluc (1729-1812). Paris, 1 October 1781. 1 page plus integral address leaf. Deluc's autograph signature from another letter tipped to the lower margin. 248 x 184 mm. Small lacuna in address leaf where seal was broken, a few pin-holes, marginal annotations in another hand, but very good. (2) [Deluc, Guillaume Antoine (1729-1812)]. Autograph manuscript (fragment from a larger work). Single sheet, 2pp., the first page numbered 13. 237 x 197 mm. Light toning, a (truncated) few small marginal stains, but very good. Marginal annotation in another hand identifying the document as by G.-A. Deluc. (1) From Swiss geologist and meteorologist Jean André Deluc to his younger brother, Guillaume Antoine. The Deluc brothers were pioneers in the field of mountain and high altitude studies; in 1770 they became the first to climb to the peak of Le Buet in the Swiss Alps (3099 meters), where they conducted the first scientific tests (of temperature and air pressure) at high altitudes. Deluc's letter to his brother touches on the political unrest in Switzerland, which had undergone a series of peasant revolts against the country's ruling cities, the last being the 1781 Chenaux revolt against the rule of Fribourg. (2) Fragment from a larger work on volcanoes, mentioning Cotopaxi and Vesuvius. G.-A. Deluc had a particular interest in volcanology; in 1757 he became the first student of volcanoes to visit and investigate the eponymous Vulcano in the Aeolian Islands. . (Inventory #: 41094)