n6 PHOTOGRAPHY FOR NATURALISTS. 



place sometimes occupied by a pad. No inconvenience 

 arises from this course, as the tissue is not inspected 

 during the printing stage. The length of exposure 

 required for a transparency which is destined to be 

 backed is obviously precisely the same as that required 

 for a print on paper. As there is rather more risk of 

 the tissue leaving its support during development, the 

 safe edge should be a substantial one. Development 

 may be conveniently performed in a basin, in which, if 

 desirable, a transparency can be left face downwards to 

 develop itself while further operations are conducted 

 above it. It is not advisable to employ alum, still less 

 formalin. The hardening of the gelatine is a distinct 

 disadvantage in a carbon transparency, as it renders it 

 brittle and, therefore, easily scratched and liable to 

 chip. 



As soon as the transparency is dry, the photo- 

 grapher will realise the advantage of this over any other 

 form of printing. He will probably first try the effect 

 of white paper as a backing : he should not, however, 

 confine himself to this. Papers of all tints and textures 

 should be experimented with. Even bright colours, 

 yellows or blues, are suitable to certain subjects. A 

 metal backing is pre-eminently adapted to fish, reptile, 

 and insect subjects to anything, in fact, whose natural 

 colour is "metallic." Again, in the case of metals, the 

 colour and texture of the backing admits of variation. 

 We may have a backing composed of polished copper, 

 an admirable one for the photographs of certain kinds 

 of carp ; or of frosted silver, which suits almost any- 



