200 THE BOOK OF THE LANTERN. 



the tank, the surface of the fluid will appear as a descending 

 line across the sheet. The strength of the developer should 

 not be so great as for ordinary development, by which I 

 mean that the proportion of iron can be conveniently 

 reduced so as to render development less sudden than it 

 generally is with chloride plates. When once the developer 

 has been poured into the tank, the red glass can be with- 

 drawn, for the ferrous oxalate developer is red enough in 

 itself to form a protection to the plate from the light. 

 Presently the image will begin to appear, and will gradually 

 gain in strength. When it is fully developed, as it will be 

 in about two minutes, the plate can be removed, washed, 

 and placed once more in the lantern in a tank of fixing solu- 

 tion. Here it will gradually get clear, as the unaltered 

 chloride is acted upon by the hyposulphite of soda solution. 



To perform this interesting experiment in the most per- 

 fect manner, a special form of tank may be employed. It 

 should have a tap at its lower part, to act as a waste pipe. 

 With this arrangement the chloride plate need not be 

 removed from the tank at any stage of the process. When 

 development is complete, the ferrous oxalate can be drawn 

 off ; then water can be poured in, to be immediately drawn 

 off and replaced by the hypo solution. 



The chloride plate employed can be put into the printing 

 frame by gaslight, provided that the operation be performed 

 with ordinary despatch. It should be noted, too, that these 

 plates, or at least some brands of them, rapidly deteriorate. 

 But the careful operator will try the experiment in private 

 before he ventures before the public, and will take care that 

 his plates are above suspicion. 



