'Air volcanoes', near Carthagena, Columbia, 1849.
© Science Museum / Science & Society Picture Library
Colour engraving by Whymper from 'Phenomena of Nature', published in London in 1849 for the Society for Promoting Christian Knowledge. 'The principal volcanoes of the earth pour forth streams of molten lava, or mineral substances in a molten state, but there are other volcanoes which send out merely water, mud or air. Examples of air volcanoes can be found near the small village of Turbaco, twenty miles from Carthagena in South America. They rise in the form of cones up to twenty-five feet high and throw out air with considerable force'.