Charles Wheatstone demonstrated his stereoscope to the Royal Society in 1838 in order to demonstrate binocular vision. Using mirrors, the device presents a pair of identical images, one to either eye, thus creating an apparently three-dimensional image to the viewer. Although Wheatstone's invention was intended to be an experimental demonstration apparatus, stereoscopes became popular scientific toys. In the early 1840s, after the invention of photography, some of the foremost early photographers such as W H Fox Talbot and Roger Fenton began producing calotypes specifically for use in stereoscopes. Stereoscopes were so popular that 250,000 were sold in Paris and London in three months in 1851.
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