THE: TRON PROCESSES 267 
Water to 125 ccm 2 oz. 
Soak, melt by heat, and add: 
Ferrous sulphate 33.3 g YZ oz. 
Glycerine 33.3 ccm YZ oz. 
Strain, and cast into flat tins. Or the following may be used: 
Gelatine 450 ¢ 1 Ib. 
Water 2550 ccm 90 oz. 
Size powder _ 450 ¢ 1 Ib. 
Iron alum 42¢ LY, oz. 
Water . 570 ccm 20 oz. 
Dissolve the gelatine in the water ; then add the size powder. 
Dissolve the alum in the water, and add to the gelatine-glue 
solution gradually, stirring all the time. Pour into tins or on 
a slab. After use it can be remelted and used again, but a 
little fresh jelly should always be added. Or the following 
(Albert) : 
Gelatine | 160 g 1228 gr. 
Glycerine 15 ccm 115 min. 
Ox-gall 25¢g 192 gr. 
Ferrous sulphate 2g 15.4 gr. 
Water to 1000 ccm 16 oz. 
Soak the gelatine in water, melt, add the other ingredients, 
and, finally, the iron salt dissolved in a little water. Cast on 
zinc which has been roughened with emery to cause it to 
adhere well. The coating should be 2mm (1/25 in.) thick. 
PLAYERTYPE.—This is a method of copying printed matter 
invented by J. H. Player, in which a sheet of sensitive paper, 
bromide or development (gaslight), is placed face down on 
the printed matter, pressed into contact and exposed through 
the back. On development a negative copy is obtained. The 
slower papers are more suitable; the paper should be pressed 
into contact by a sheet of plate glass, and the latter covered 
with a yellow filter which can be made by immersing fixed out 
