'The Dropping Well', 1849.
© Science Museum / Science & Society Picture Library
Colour engraving by Josiah Wood Whymper from 'Phenomena of Nature', published in London in 1849 for the Society for Promoting Christian Knowledge. 'Spring-water generally contains certain mineral substances, gathered from the soil through which the water flows. It is owing to these mineral substances that many springs have the property of petrifying objects, that is covering them entirely with a stony crust which makes them appear as if turned to stone. The Dropping Well in Knaresborough, Yorkshire, is one of our most noted petrifying springs.'