INSTANTANEOUS PHOTOGEAPHY. 25 



fits into a hole in a lever fastened to the armature of an electro- 

 magnet, M, when the contact-brush on B rests on the insulation 

 between segments 24 and 1. (See Fig. 11.) The armature- 

 lever is held up by a spring until drawn away by the greater 

 force of the electro-magnet, when an electric current is sent 

 through its coils. By an ingenious mechanical arrangement, to 

 which we shall refer more particularly hereafter, when the arma- 

 ture is drawn the loose collar is thrown into gear with a second 

 collar fast to the shaft ; and if the shaft is in motion the brush is 

 thereby carried around over the periphery of the ring S, making 

 contact with each of the brass segments successively. The posi- 

 tion of the contact-motor in the camera-house is shown at M, 

 Fig.l. 



An insulated copper wire leads from each of the twenty-four 

 binding-posts, P, to the releasing magnet of the large exposor, L, 

 of the same number, while a second wire passes from each of the 

 first twelve of them (P 1 to 12) to a double binding-post, D, 

 stamped with the same number. Two cables, G and H, each over 

 one hundred feet long and composed of thirteen wires, connect at 

 one end to the double binding-posts, and at the other end twelve 

 of the wires to the releasing magnet of each series of portable 

 exposors, F and F, the thirteenth serving as the return wire to 

 D, R, from each series as shown in the diagram. Another wire 

 from D, R, carries the return current from both series of small 

 exposors to a separate binding-post, P R, to which also a wire with 

 twenty-four branches conducts the return current from the large 

 series of exposors. 



With the connections made, as just described, a portable battery 

 of cameras could be moved at a moment's notice, as was often 

 necessary, from one part of the field to any other within a radius 

 of one hundred feet of the double bihding-posts ; and at the 

 Zoological Gardens, on some few occasions, when only one series 

 of exposures was desired, the cables were connected end to end, 

 and then with the operating apparatus at one station the cameras 

 could be moved in any direction to places two hundred feet 

 distant. 



The electrical battery, C, which furnished the motive-power for 

 operating the magnets, consisted of fifty-four Le Clanche (prism) 

 cells, usually arranged in a multiple arc of three series of eighteen 



