12 
ANIMALS IN MOTION. 
B, the lateral background, divided by threads into 
spaces five centimetres, or about two inches, square, 
every tenth thread being of greater thickness than the 
others. At C C were portable backgrounds divided into 
similar squares, and placed close to and at right angles 
with the lateral background, when a fore-shortened series 
of exposures rendered them necessary. These back¬ 
grounds were black or white, as circumstances required. 
T T, the track, covered with corrugated rubber matting, 
along which the animal was caused to move. L, a lateral 
battery of twenty-four automatic electro-photographic 
cameras, arranged parallel with the line of progressive 
motion ; these were so placed that each camera was 
practically opposite the animal when its phase of move¬ 
ment was photographed. R, an automatic electro-photo¬ 
graphic camera with twelve lenses, the plate-holders being 
adapted for a plate three inches wide and thirty-six inches 
long, which, in practice, it was found convenient to divide 
into three parts of twelve inches each. A supplementary 
lens was arranged to permit focussing while the plate- 
holder was in position. For fore-shortenings at an angle 
of ninety degrees to the laterals, this camera was usually 
placed on end, so as to obtain one vertical line of view 
for the series of twelve exposures. F, a similar camera 
to R, usually placed horizontally at any convenient point. 
D, the station of the director, and where were also placed 
the electric batteries, the motor-clock for intermittently 
completing the electric circuits, the chronograph for 
recording the intervals of time between each successive 
exposure, and other apparatus connected with the work. 
The motive power of the circuit-maker was an adjust¬ 
able weight attached to a cord wound round a drum, the 
speed being regulated, partially, by a fan-wheel. 
Fastened to the frame of the motor-clock was a 
ring of hard rubber, in which were inserted twenty-four 
insulated segments of platinum; these segments were 
connected by insulated wires to the same number of 
binding-posts. A shaft, connected by an arrangement 
of geared wheels, passed through the centre of the 
segmented ring and carried a loose collar; a stout metal 
rod was firmly attached near its longitudinal centre to 
this loose collar. One arm of the rod carried a laminated 
metal scraper, or contact-brush, arranged to travel around 
the periphery of the ring, and in its revolution to make 
contact with each segment in succession. The contact¬ 
brush was connected, through its arm, with one pole of 
the battery ; and each segment, through its independent 
wire and magnet of its electro-exposer, with the other pole. 
When twenty-four consecutive phases of an act of 
motion were to be photographed, all of the insulated seg¬ 
ments of the ring were put in circuit. When twelve 
consecutive phases were to be made synchronously from 
each of two or three points of view, each alternate seg¬ 
ment was placed in circuit with the electric battery, and 
the proper connections made with each set of exposers 
in front of the lenses. 
An experimental trial having been made to ascertain 
the time required by the animal or model to complete 
the intended movement, the weights and fan-wheel were 
adjusted to cause the contact-brush to sweep around the 
