( ê ) 



in the developer or by the addition of potassium bromide. That only 

 the rapidity of reaction of the developer is reduced, I was able to 

 ascertain by the so-called neutralisation of solarization with a de- 

 veloper (rodinal 1 in 10) at a lower temperature. First a normal 

 copy is developed, which when development is continued, turns into 

 a polarized one. 



However, the normal copy obtained in this way, differs very 

 much from an ordinary one. When viewed by light reflected at an 

 angle, it is just in the densest portions that the surface is found to 

 have the highest gloss; consequently here the grains do not lie 

 against the surface. After the copy has changed into a polarized 

 one, in which the polarized depth image predominates, the surface 

 remains unchanged, and now shows the highest gloss in the clear 

 portions. Consequently the surface image has not undergone a rever- 

 sion of density proportions, from which it follows that the normal 

 copy obtained by retarded development must be the solarized image 1 ). 

 This cannot be ascribed to a change of the solarization, i.e. to a 

 change in the substance of the solarized latent image. 



Consequently in the surface glass we have a means of ascertaining 

 in the case of solarization, whether an agent reacts upon the sub- 

 stance of the latent image or upon the development. Thus I could 

 ascertain inter alia, that chromic acid mentioned by J. M. Eder 8 ) 

 and ammonium persulphate referred to by K. Schaum and W. Braum, 

 which both exercise a hardening influence upon the gelatine, at the 

 same time also react upon the substance of the latent image in the 

 case of solarization, by which it is reduced to the substance of the 

 ordinary latent image. 



III. Sabatier's polarization. 



If during the development of a plate light is admitted, three 

 different phenomena may occur: 



1. If a very slight amount of light is admitted, the plate in the 

 developer shows an increase of reducibleness. 



i) It stands to reason that during the appearance of the normal copy in the 



developer, consequently before polarization sets in, development of the non-solarized 



silver haloid in the lower layers may take place. Consequently it is better to say 



tbat the solarized image is only formed within a certain definite time of development. 



2) Pbot. Korresp. 1902; S. 647. 



J. M. Eder. Jahrb. f. Phot. u. Repr. 1903; S. 23. 



J. M. Eder. u. E. Valexta. Beitrage zur Photochemie. 1904; II; S. 168. 

 J. M. Eder. Handb. d. Phot. 1903. Bd. Ill; S. 828. 

 3} Pbot. Mitt. 1902; S. 224. 



