'The Seven-headed Hydra', 1806.
© Science Museum / Science & Society Picture Library
Engraving by J Chapman of the many-headed monster of Greek mythology. To kill the monster was the second labour of Hercules. He did this by cutting off each head and then burning the neck to prevent two new heads appearing. Illustration from 'Encyclopaedia Londinensis, or, Universal Dictionary of Arts, Sciences, and Literature' published in London, 1810-1829.