[Reynaud de Montlozier, Fr. - Dominique]; - Essai sur la théorie des volcans d'Auvergne. Riom et Clermont, Landriot et Rousset, 1802. In-8 uncut paperback, untrimmed, in a period cover. - 184 pp. Second edition (the first one in 1789) of this important treatise on volcanology which is based on numerous observations on the field that he surveyed for many years. Also included: Lacoste, Pierre-François. - Mineralogical and geological letters on the volcanoes of Auvergne, written during a trip made in 1804. Clermont, Landriot, 1805. In-8, paperback in original dust jacket, uncut, untrimmed - [4 ff.], IX, 459 pp. and [3 pp.]. 2 large folding tables (non-volcanic and volcanic minerals). The work is a collection of 45 letters dedicated to the Auvergne. The first 8 concern the Dôme mountains, the next 21 the Golden mountains and the last 16 describe the Cantal. Lacoste (1754-1825) was a naturalist who taught natural history at the central school of Puy-de-Dôme and directed the botanical garden there.