The public’s phenomenal interest in this device erupted after Queen Victoria became delighted with it at the Crystal Palace Exposition in 1851. The machine allowed the viewer to see a three-dimensional image of a photograph placed in the unit’s wire holder. On the special stereoscope cards (called stereographs) two images of the same object appeared side by side. The images were taken with a single camera that had two lenses placed two-and-a-half inches apart; the same as the distance between a person’s eyes. When the viewer looked through the stereoscope, the image seemed to “pop out” at him. Millions of stereographs were mass-produced. The pictures allowed individuals to travel the world and witness some of the most amazing attractions in the comfort of their own homes. Among the most popular stereographs were images from the European countryside, the pyramids of Egypt, and views from New York, Chicago, and San Francisco.