and on the Formation of Mountain Chains and Volcanos, as the Effect of the Same Power by Which Continents are Elevated. [Read March 7th, 1838]. Plate XLIX.[London: Geological Society : 1839]. in- 4 ; br. (260 x 212 mm) (288 x 232 mm). Édition constituée par le tiré à part de la revue Geological Society. (pp.601-631). 3 figures in-texte, une carte de l’Amérique du Sud et 1 f. d’explication des planches. Darwin was keen not only to produce the official reports on the geology observed on the Beagle voyage, but also to underpin it with ‘an ambitious causal explanation of continental elevation, which would in turn fit into an even more ambitious ... geotheory of endlessly rising and subsiding crustal plates’ (Rudwick p.493). Darwin’s remarkable attempt to develo a global tectonic (Rhodes p.193) was read to the Geological Society on 7 March 1838. A summary, without illustration, was published in the society’s Proceedings II, no. 56, 1838, pp.654-660. Darwin revised the paper and the final version was published in the Society’s Transactions 2nd Ser., V, 3, on 21 February 1840. The present work is printed on the same sheets, but the details on the inserted slip present here are reset from those incorporated in p.16 of the ‘Explanation of the Plates and Woodcuts’ in the Transactions. The Council Minutes in the Geological Society’s archives for 18 December 1839 reveal that only 15 copies were offprinted (CM 1/5 p.252). This is confirmed by cross-referencing the society’s ledgers (FIN 1/2 p.215). EXCEPTIONALLY RARE, ‘IT IS THE SINGLE MOST IMPORTANT ARTICLE FOR UNDERSTANDING [DARWIN’S] INTELLECTUAL POSITION [ON GEOLOGY]’ (Herbert, p.225). Not in Freeman (his 1656 is the serial publication, giving the incorrect number of illustrations and omitting the map). Sandra Herbert, Charles Darwin, Geologist, 2005, pp.217-232; Frank H.T. Rhodes, ‘Darwin’s search for a theory of the Earth’ in BJHS, 1991, 24, pp.193-229; Martin J.S. Rudwick, Worlds Before Adam, 2008, pp.492-3.