Stereoscopic photograph of Snake-Exhibitors in Calcutta, 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), "The largest snake we see here is a small python, non-venomous and easily tamed. The smallest is the deadly "Russell's viper." You can easily distinguish the widely-known cobra (cobra de capello), the venomous species which is responsible for the death of twenty thousand people annually. He is easily known by his erect striking attitude and by the flattened condition of his neck, which always assumes this form when he is enraged and ready to make an attack. There is a dark figure on the back of the flattened neck which is called the "spectacles" because of its semblence to a pair of spectacles, but in this view it is only partially seen...Venomous show-snakes usually have their fangs removed, and these fellows are snake-exhibitors rather than snake-charmers." 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.