NEST-PHOTOGRAPHY. 31 



much over exposed, but so they were before, while 

 now the darker portions of the subject have made 

 their presence felt, and if we use a weak developer, 

 will come up not now hopelessly behind the others. 

 If the gloom is very deep it may be further 

 counteracted by throwing reflected light down 

 into the hollow. For this it is preferable to use 

 the polished surface of a dark-slide or the ground- 

 glass screen, a silvered mirror throwing rather too 

 strong a light. The general photographer will 

 shudder at the suggestion of waving a dark-slide 

 about in the sun-light ; but, although a severe test 

 of its light-tightness, unless it is able to endure 

 it without showing a suspicion of fog on the plate 

 it is not fit for our work, in which the slide will 

 often have to remain in position at the camera 

 back for hours at a time awaiting the bird's return. 

 Such artificial illumination must be used sparingly, 

 or by destroying all shadow it will bring about 

 a flat and uninteresting result. The reflected rays 

 must be kept moving throughout the exposure, 

 never being allowed to come to rest on any part, 

 or it will inevitably produce a light and unnatural 

 patch in the print. 



Sometimes in caves and in gloomy fissures in 

 rocks there is so little light that one cannot see 

 any image on the ground-glass by which to focus. 

 In this case it is a good plan to stick a lighted 



