'Water Spouts', 1849.
© Science Museum / Science & Society Picture Library
Engraving by Josiah Wood Whymper (1813-1903) taken from 'Phenomena of Nature', published in London in 1849 for the Society for Promoting Christian Knowledge. 'The first symptom of a water spout (sea-whirlwind) is usually a violent disturbance of the sea immediately below a dark cloud. Waves are whirled into a mas up to a hundred yards in diameter, which then rises with a spiral movement in a conical shape toward the cloud, which in turn produces a cone of its own. These two cones gradually approach each other until they unite and are carried to and fro by the wind'. In fact the spout does not actually consist of water sucked up from the surface, but is actually water vapour condensing in the core of a rapidly revolving vortex of intense low presure.