January 1832

Darwin was excited by his first port of call, where he started making comprehensive notes, observations and collections on a wide range of environmental features despite the barren nature of the landscape. It was here that he first realised the opportunities that would be afforded to him by the voyage in terms of geology and natural history.

Darwin observed atmospheric dust in the Cape Verde Islands and considered its origins:

“the atmosphere is generally very hazy … chiefly due to an impalpable dust, which is constantly falling, even on vessels far out at sea. … It is produced, as I believe, from the wear and tear of volcanic rocks, and must come from the coast of Africa.”*

He also observed the habits of marine animals and collected many specimens. He wrote in detail about two molluscs — the sea slug Aplysia and cuttlefish (octopus). Both creatures have colourful defence mechanism, which Darwin observed and noted in detail. Sea slugs release a coloured fluid that stains the water around it. The cuttlefish has a similar defence mechanism, and are also known as the chameleons of the sea for their use of camouflage to avoid predators.

Find out about atmospheric science, ocean science and geology on our science pages.

*Darwin, C. R. Voyages of the Adventure and Beagle Vol. III. Journal and remarks. 1832–1836. (Henry Colburn, 1839); via van Wyhe, J. (ed.) The Complete Work of Charles Darwin Online (http://darwin-online.org.uk, 2002).