Record. lxv 



from its wrapping into the lighted room and placed in the 

 slide holder. After exposure, it is taken out into the light 

 and placed in the developing bath, and the picture is then 

 developed in the light, and may be fixed in the light. Of 

 course during the changes the plate should be shielded from 

 the light as much as is feasible, and the fixing bath may 

 always be covered. But all of the operations may be carried 

 on without any dark-room conveniences that may not be 

 secured even in the open fields. 



When weak hydrochinone baths are used, the picture, when 

 developed in strong lamp light, or in sunlight, has at first a 

 golden yellow color. When left in the lighted bath for an 

 hour and a half, it slowly darkens to a nearly normal shade, 

 as the details come out more sharply. If the exposure has 

 been correctly made, there will be no trace of fog. With 

 stronger baths, the picture comes out in the normal time, and 

 has the normal shade. 



If the pictures are too dense, the remedy is to reduce the 

 strength of the sodium carbonate solution, or to increase the 

 amount of hypo in the bath. Very fine results are obtained 

 with the sodium carbonate solution at half the strength given 

 in Cramer's formula. 



When the plate has been sufficiently exposed, a negative 

 of the object can usually be seen upon the plate before 

 development. With long exposure this image is very distinct. 

 It fades out in the bath, and the plate becomes clear. The 

 shadows appear strongly but indistinctly at first, and of a pink 

 color, and the high lights still appear white. The solution 

 remains clear. Too much hypo will cause turbidity and a 

 loss of detail. 



When the plate is exposed in a printing frame under either 

 a negative or a positive, an exposure of half a minute to dif- 

 fuse daylight is ample, with an ordinary negative. The 

 plate may be overexposed by placing it for a long time in 

 direct sunlight, and it will then appear on development some- 

 what like an overexposed negative. This has not yet been 

 tried with hypo in the bath. 



Professor Nipher showed a preliminary diagram in which 

 exposure and illumination of the developing bath were taken 



