INSTANTANEOUS PHOTOGRAPHY. 



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the Zoological Society, the thoroughbred horses at the Gentle- 

 men's Driving Park, and the human subjects, carriage- and 

 saddle-horses, and other domestic animals in the studio at the 

 University of Pennsylvania. This out-door studio was built on 

 the grounds surrounding the University Hospital, far enough 

 away from a principal thoroughfare to be undisturbed by pass- 

 ers-by. Its ground-plan, diagrammed in Fig. 1, was somewhat 



Fig. 1. 



similar in shape to a semicircle. On the north side the diameter 

 of the semicircle was a shed. A, B, one hundred and twenty feet 

 long, eleven feet high, and sixteen feet deep, painted black. The 

 greater portion of its front, D, G, from the edge of the roof to 

 the ground, was covered by a net-work of white threads, accurately 

 vertical and horizontal, and five centimetres (almost two inches) 

 a})art, every tenth thread being thicker than the rest. Directly 

 in front of this background ran a level track, H, J, eight feet 

 wide, covered down the centre with heavy corrugated rubber 

 matting, K, N. Each end of the track was closed by a double 

 gate, O, painted black, in front of which hung an adjustable series 

 of vertical threads, H and J, five centimetres apart, every sixth 

 thread being thicker than the rest. 



On the opposite or southern side of the enclosure was the 

 camera-house E., a long, low structure with white front, forming, 

 as it were, a chord in the semicircle of the fence P, wdiich ex- 

 tended from each end of it to the ends of the track. The fence 

 was built in this shape and slanting outward at the top, and the 



2 



