All Intensive Purposes

This will be Wikipedia's image of the day on December 21. (You can find it the "archives" for this month; scroll down to the 21st.) Wikipedia explains that it is:

An animated image of Eadweard Muybridge's pioneering high speed photography, demonstrating that a horse's feet all leave the ground during a gallop. Muybridge used a battery of cameras lined along a track. The first camera had to be triggered manually, but the rest were automatically triggered by an electronic apparatus he designed.

Rebecca Solnit's River Of Shadows, which is about Muybridge and these photos, among other things, is a tremendous book and well worth reading.