Brian Rosen (Zoology) and Jill Darrell (Palaeontology) have just published a paper on Darwin’s coral specimen collections and specimen lists. Darwin examined coral reefs in detail during the voyage of HMS Beagle, describing the different types of reef and using this information to write one of his early scientific works The Structure and Distribution of Coral Reefs.
They were invited to present a talk on this subject at a conference on Darwin’s work at the Universita G. d’Annunzio, Chieti-Pescara, in November 2009. The paper deals with the only known Darwin geological collection in the Museum that comprises 29 coral reef specimens (held in Zoology), almost all from Cocos (Keeling) atoll in the Indian Ocean and accompanied by a little known and hitherto enigmatic Coral Reef Specimen List (holograph held in the NHM Library). Darwin mentions his visit to Keeling and interest in corals in a letter to his sister, sent from Mauritius.
Darwin distinguished three primary types of reef: atolls, barrier reefs and fringing reefs, and used his own observations and those from FitzRoy's surveys to explain what he thought were the reasons for the existence of atolls - including Keeling, which he examined in detail. Darwin noticed that reef-building corals did not grow below a certain depth of water, but that atolls isolated from other rocky islands were reasonably common. He rejected the idea that gradual sediment buildup had provided foundations, and said that the idea of so many isolated sea-mounts of the right depth in the middle ocean for coral growth could be rejected. He argued that rocky islands had sunk gradually below the surface, leaving their original coral reefs to keep the same level as the surface of the sea. Darwin thought that earthquakes might be connected with the sinking islands - he did not know then what we know about plate tectonics, but had developed a keen interest in geological uplift and subsidence in South America on an earlier part of the voyage.
Brian and Jill offer for the first time a plausible explanation of the true origin and purpose of this list and set of specimens. The specimens are unusual, if not unique, in being a small exhibit prepared by Darwin himself, at or before the time he donated them. The most likely occasion for which Darwin prepared his exhibit was that of his first presentation of his famous subsidence theory of coral reefs to the Geological Society of London on May 31st 1837.
Rosen B. R & Darrell, J. 2011. A generalized historical trajectory for Charles Darwin’s specimen collections, with a case study of his coral reef specimen list in the Natural History Museum, London. In: Stoppa, Francesco & Veraldi, Roberto, Eds., Darwin tra scienza, storia e società. 150° anniversario della publicazione di Origine delle Specie [= Darwin in science, history and society. 150th anniversary of the Origin of Species.] Edizioni Universitairie Romane, Roma, pp.133-198.