Stereoscopic photograph of cows on the pavement of Harrison street in Calcutta in West Bengal, taken by James Ricalton in c. 1903, from The Underwood Travel Library: Stereoscopic Views of India. This image is described by Ricalton in 'India Through the Stereoscope' (1907), "Did you ever before see so many animals apparently in a state of supreme bliss?...They not only command the sidewalk, but they command the street; they occupy temples and shops; they walk into private homes; they stampede the sweetmeat stalls and partake, unrestrained and unchastised, of all the "sweeties." Their license is unrestricted; their authority is unquestioned; they have the freedom of the city." This is one of a series of 100 photographs, designed to be viewed through a special binocular viewer, producing a 3D effect. The series was sold together with a book of descriptions and a map with precise locations to enable the 'traveller' to imagine that he was touring around India. Stereoscopic cameras, those with two lenses and the ability to take two photographs at the same time, were introduced in the mid 19th century and revolutionised photography. They cut down exposure time and thus allowed for some movement in the image without blurring as subjects were not required to sit for long periods to produce sharp results.