Wiki: "In 1872, the former governor of California, Leland Stanford, a businessman and race-horse owner, hired Muybridge for some photographic studies. He had taken a position on a popularly debated question of the day — whether all four feet of a horse were off the ground at the same time while trotting. In 1872, Muybridge began experimenting with an array of 12 cameras photographing a galloping horse in a sequence of shots. His initial efforts seemed to prove that Stanford was right, but he didn’t have the process perfected. The same question had arisen about the actions of horses during a gallop. The human eye could not break down the action at the quick gaits of the trot and gallop. Up until this time, most artists painted horses at a trot with one foot always on the ground...Between 1878 and 1884, Muybridge perfected his method of horses in motion, proving that they do have all four hooves off the ground during their running stride. In 1872, Muybridge settled Stanford's question with a single photographic negative showing his Standardbred trotting horse named Occident, airborne at the trot."
