'Petrifying Springs', 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. 'In volcanic regions, or those where earthquakes have occurred at a comparatively recent date, springs are frequently loaded with mineral substances which they deposit abundantly in their course, sometimes in such quantities as to form solid mases many feet thick. Extensive layers of this stony substance can often extend to over a mile in length'.