The Geology of Ascension and St. Helena Islands

Extract

The writings of Charles Darwin, Renard, Mellis, Reinisch, and others have already made the salient features of lonely Ascension and St. Helena accessible, if not familiar, to geologists— St. Helena has won the surprised interest of biologists, who have long speculated on the origin of its unique species of plants and animals. From each island collections of rocks have been made. Following Renard's well-known contribution to the petrography of Ascension (“Challenger” Reports, Physics and Chemistry, vol. ii, 1889), Reinisch's paper in the Report of the Deutsche Siidpolar Expedition (1901–3) gives a large number of petrographical. descriptions, including a goodly number of chemical analyses. No adequate geological map of either island has, however, been published, nor, indeed, was this really possible before the British Admiralty had issued the greatly improved chart (No. 1691) of Ascension, in 1910, with corrections added to the year 1921, and the British War Office had issued its excellent contour-map of St. Helena, dated 1904. Each map is on a large scale. Even, though lacking contour lines, the Ascension chart was obviously to be of service to anyone attempting a reconnaisance survey of that island.