Muybridge visited Marey in 1880, with his pictures of horse locomotion. Marey asked him if he could photograph birds in flight. Muybridge told him he had no success so far. Marey then invented a "photographic gun" for the purpose. The "gun" had a rifle-like sight and a clock-mechanism so that when the shutter was tripped it made twelve exposures of 1/72nd of a second each.