46 ELEMENTARY PHOTO-MICROGRAPHY. 



Potassium bromide ... i oz. at 2d. oz. 

 ferricyanide i oz. 3d. oz. 

 carbonate 4 ozs. 6d. Ib. 

 metabisulphite 2 ozs. 3d. oz 

 Sodium carbonate 



(washing soda will do) i Ib. 4d. Ib. 

 Sodium hyposulphite 7 Ibs. 2d. Ib. 

 sulphite ... ilb. 6d. Ib. 



hydrate ... i oz. 2d. oz. 



Some brands of plates have a tendency to frill 

 and pucker at the edges, more particularly in warm 

 weather, which, if not stopped in time, will result 

 in the film separating from the plate. Soft gelatine 

 or prolonged development or washing may cause it. 

 The best way, of course, is to reject any kind 

 of plate that constantly gives this trouble, but it 

 may be prevented by first rubbing the edges of 

 the plate with a wax candle before the developer is 

 poured on. This will keep the liquid from pene- 

 trating between the film and the glass. 



The following kinds of plates will be found 

 satisfactory : 



For low powers (slow), " Castle." } (Mawson 

 For high powers (rapid), " Electric." ) and Swan.) 

 For sections, " Process." (Ilford.) 

 For colour contrasts, " Chromatic." (Ilford.) 

 For lantern slides, "Special" and "Alpha." 

 (Ilford.) 



The " Special " Ilford plate gives warm and cold 

 tones of black, and the " Alpha " gives browns and 



