Thomas Young is best remembered for his discovery of the principle of interference (otherwise known as the principle of superposition). In 1800, Young was left a house and a great fortune in London, where he moved to and set up his own medical practice. He was interested in a number of scientific fields and he was able to follow these however he wished due to his wealth. His early work concentrated on the physiology of vision, where he realized that the eye focuses on distant and near objects by changing the shape of its lens (1801). He also showed that colour blindness was due to the eye's inability to recognize one of three colours, red, green and violet (work later extended by Helmholtz and James Clerk Maxwell) and that these colours were detected by cones in the retina. In 1801, Young discovered the principle of interference, suggesting that bands of fringes were caused by light waves interfering with each other. He verified this experimentally by observing the patterns created when light passed through very small apertures. Young was involved in many other aspects of science, for example, in the field of materials by developing the idea of an elastic modulus, the ratio of stress of a material to its strain. His knowledge of hieroglyphics allowed him to make an important contribution to Egyptology, through the translation of the text on the Rosetta Stone.
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