Appendix I 159 



book illustrations, but the graduations appear to be carelessly made. 

 It is, however, the most convenient and handy camera and appliance 

 for this purpose, and saves its cost very quickly, inasmuch as more 

 and better work can be done by its aid. It is illustrated in Fig. 1 16. 



The best plates to use are those prepared by certain firms 

 specially for the manufacture of process blocks. For apparatus and 

 similar work Ilford " half-tone " plates have been found most satis- 

 factory, while for the photography of diagrams, sketches, book 

 illustrations in black and white, etc., Ilford " Process " plates cannot 

 be excelled. The whole success of lantern-slide making (i.e. line 

 work) depends upon securing a negative giving the sharpest possible 

 contrasts, and as most plates are made with the expressed intention 

 of toning down sharp contrasts, it follows that a special plate is 

 necessary. Any one who has tried to make good slides with 

 ordinary plates will know the practical impossibility of doing so, 

 while no process could be more simple, more certain, and more 

 pleasing in its results than the following one, provided the above 

 plates be used. " Quarter " plates will be found the most suitable 

 for our purpose, having one dimension identical with that of the 

 finished slide, which is 3^ inches square. 



The plate having been exposed it is removed to the dark room, 

 placed in a developing dish, and swilled over from corner to corner, 

 with a mixture of the following solutions ; care being taken to 

 avoid air-bubbles, and rocking the plate and dish until the picture 

 appears, darkens, and disappears : 



Water 30 fluid ozs. . , 850 c.c. 



Hydroquinone . . 150 grains. . . 10 grams. 



Metol 30 grains ... 2 grams. 



Sulphite of soda . . 3| ozs 100 grams. 



i Water 30 fluid ozs. . . 850 c.c. 



B 1 Carbonate of potash 6 ozs 170 grams. 



I Bromide of potash . go grains . . . 6 grams. 



, rWater 10 fluid ozs. . . 280 c.c. 



\Citrate of soda . . 150 grains . . 10 grams. 



For development mix 

 of A 2 ozs. or 50 c.c. 

 of B 2 ozs. or 50 c.c. 

 cf C 20 drops or i c.c. 



Development will proceed without the addition of C, but the plate 

 will be more transparent, and the contrasts much less distinct. 



