Nipher — Positive Photography: Eclipse Work. 213 



cent, solution of potassium bromide 1. If the contrasts are 

 too strong, a few drops of ammonia may be added. 



This developer was said to produce a positive in the dark 

 room, with ordinary exposure. It was hoped that this urea 

 salt either in the Waterhouse developer, or in some other, 

 and with development in the light, might shorten the camera 

 time very greatly. 



When the exposure is normal for a negative, and the plate 

 is developed in the dark room with this developer, it is found 

 that a yellow to orange coloration appears in the shadows. 

 If there are contrasts on the object, the high-lights look as 

 they do in an ordinary negative. The roof of a building and 

 the sides lighted by direct sunlight appear as in an ordinary 

 negative. Light and dark strips of slate will appear reversed. 

 The sky is dark. The sides in shadow are of a yellow or 

 orange color, sometimes almost red, and appear as positives. 

 If the exposure is increased somewhat either by an increase 

 in time, by stronger illumination of the object, or by using a 

 larger stop opening, the coloration disappears, and the whole 

 picture is seen to be a negative. A still greater exposure 

 being made, the picture approaches, and finally becomes a 

 zero result. Nothing develops on the plate. With a still 

 longer exposure the picture is reversed, and a real positive 

 develops. This picture can be developed in the light. 

 This is not the case with the Waterhouse pictures. They 

 look like positives, as any negative may be made to look like 

 a positive, but they should be called pseudo-positives. They 

 are not due to a real reversal. They are moreover somewhat 

 disappointing in appearance. It is only too evident that this 

 Waterhouse process does not seem to be a very promising field 

 for application to eclipse photography, although it presents 

 some very interesting illustrations of different forms of silver. 



The most promising field for investigation at present con- 

 sists in the application of some transforming process to the 

 film, after it comes from the camera, and before the picture 

 is developed. Various oxidizing agents have been tried with 

 different degrees of success. The most satisfactory of these 

 oxidizing solutions is a mixture of nitric acid and potassium 

 bichromate in rather dilute solution. There is no trouble in 



