The Thames in Stereographs
The stereoscopic viewer and the stereographic print derive from the "reflecting stereoscope" invented by the British physicist Charles Wheatstone in 1832. Wheatstone first made twin drawings of an object, each mimicking the perspective of the left or right eye, respectively. With the use of mirrors, Wheatstone's device then combined the pictures into a single, three-dimensional image. Soon after the arrival of photography in 1839, Wheatstone's drawings were replaced by photographs. Though initially the device used one-of-a-kind daguerreotypes, with the introduction of glass-plate negatives in 1851 stereographs could be mass-produced.
Generally, a stereograph was a four-by-seven-inch rectangular card with two photographs, usually albumen prints, mounted next to each other. As with Wheatstone's device, the pictures are made by a dual-lens camera with the centers of the two lenses placed at the same distance from each other as the centers of two human eyes. In the examples exhibited here, note how the photographs are not identical but show a slight lateral shift.
Between 1860 and 1890, as many as twelve thousand stereo-photographers took between 3.5 and 4.5 million individual images, which were printed on approximately 400 million stereographs. Often the name of the photographer or publisher, along with a short caption, was printed on the front of the card, with a longer text on the reverse. Stereographs were sold at tourist spots, from storefronts, through mail-order catalogues, and door to door. By the close of the nineteenth century, stereoscopic viewing had come within reach of a broad middle-class audience, fulfilling the London Stereoscopic Company's motto, "A Stereoscope in Every Home."
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