Origin of the Author's Investigations--Diagram of the Studio at the University of Pennsylvania where the Investigation was conducted--Batteries of Cameras, Electro-exposers, Contact-motor, Chronograph, and other apparatus used for photographing consecutive phases of animal movements--Method of obtaining successive exposures of moving objects synchronously from several different points of view--Normal Locomotion of Animals--Twelve consecutive phases of a single step of the Horse while walking; also of the Ox, Elk, Goat, Buffalo, and other cloven-footed animals; the Lion, Elephant, Camel, Dog, and other soft-footed animals; of the Sloth while suspended by its claws, and of the Child while crawling on the ground; of man walking erect--The Normal Method of Locomotion by all animals essentially the same--The Quadrupedal Walk as interpreted by Prehistoric Man, by the Egyptians, Assyrians, Phoenicians, Etruscans, Greeks, Romans, Byzantines, and by eminent artists of mediæval and of modern times--The Statue of Marcus Aurelius the great source of modern errors; Marcus Aurelius in London, Edinburgh, Glasgow, Dublin, Paris, Berlin, Amsterdam, New York, Boston, and many other cities--Albert Durer, Verrocchio, Meissonier, Paul Delaroche, Landseer, Rosa Bonheur, Elizabeth Thompson Butler, &c.--Other Quadrupedal movements, the Amble, Rack, Trot and Canter--Twelve phases in the Gallop of a Horse--Origin of the modern representation of the Gallop--Gallop as depicted by the Hittites, North American Indians, Egyptians, Assyrians, Greeks, the mediæval artists--The modern conventional gallop; evidences of its absurdity; acknowledgment by the Artist of the necessity of reformation--Leap of the Horse, Kick of the Mule, &c., all illustrated by photographs the size of life, from nature, and comparisons made with the interpretation of the same movements by artists of pre-historic, ancient, mediæval and modern times--Demonstration of the action of the primary feathers in the wing of a Bird while Flying, and a solution of the complex problem of Soaring. AFTER THE VARIOUS METHODS OF LOCOMOTION HAVE BEEN DEMONSTRATED BY ANALYSIS, THEY WILL BE REPRESENTED SYNTHETICALLY BY THE ZOOPRAXISCOPE. _Among the many Institutions where Mr. Muybridge has had the honor of Lecturing on_ ZOOPRAXOGRAPHY _are the following_:--