containing more than 20,000 figures of men, women, and children, animals and birds, actively engaged in walking, galloping, flying, working, jumping, fighting, dancing, playing at base-ball, cricket, and other athletic games, or other actions incidental to every-day life, which illustrate motion or the play of muscles. These sheets of illustrations are conventionally called "plates." EACH PLATE IS COMPLETE IN ITSELF WITHOUT REFERENCE TO ANY OTHER PLATE, and illustrates the successive phases of a single action, photographed with automatic electro-photographic apparatus at regulated and accurately recorded intervals of time, _consecutively_ from one point of view; or, _consecutively_ AND _synchronously_ from _two_, or from _three_ points of view. A series of twelve consecutive exposures, from each of the three points of view, are represented by an outline tracing on a small scale of plate 579, a complete stride of a horse walking; the intervals of exposures are recorded as being one hundred and twenty-six one-thousandths of a second. [Illustration: REDUCED OUTLINE TRACING OF PLATE 579.--"ANIMAL LOCOMOTION."] [Illustration: REDUCED TRACING OF SOME PHASES FROM PLATE 758.] [Illustration: REDUCED TRACINGS OF PLATE 347.] When one of the series of foreshortenings is made at a right angle with the lateral series the arrangement of the phases is usually thus: 1 2 3 4 5 6 7 8 9 10 11 12 Laterals. 1 2 3 4 5 6 7 8 9 10 11 12 Rear Foreshortenings from points of view on the same vertical line, at an angle of 90 deg. from the Laterals. 1 2 3 4 5 6 7 8 9 10 11 12 Front Foreshortenings from points of view on the same horizontal plane, at suitable angles from the Laterals. The plates are not _photographs_ in the common acceptation of the word, but are printed in PERMANENT INK, from gelatinised copper-plates, by the New York Photo-Gravure Company, on thick linen plate-paper. The size of the paper is 45 × 60 centimetres--(19 × 24 inches), and the printed surface varies from 15 × 45 to 20 × 30 centimetres--(6 × 18 to 9 × 12 inches). The number of figures on each plate varies from 12 to 36. To publish so great a number of plates as one undivided work was considered unnecessary, for each subject tells its own story; and inexpedient, for it would defeat the object which the University had in view, and limit its acquisition to wealthy individuals, large Libraries, or Institutions where it would be beyond the reach of many who might desire to study it.