( 12 ) 



ning of a decrease in reducibleness is smaller than is necessary for 

 a beginning of an increase of this power luith the original condition 

 of the silver bromide. 



V. The theory of the latent image. 



In the case of the theory of the latent image two facts have to 

 be observed, which are directly connected with each other : 



1. The action of the light upon the silver haloids; 



2. The physical or the physical and chemical changes in the silver 

 haloid resulting from this action. 



The theory proper of the latent image is only restricted to the 

 latter, consequently comprises only secondary phenomena. Of all 

 the theories enunciated, only the subhaloid theory of Choiselat and 

 Ratel l ) has maintained itself, especially owing to the subsequent 

 investigations of M. Carey Lea 2 ), H. Weiss 3 ), J. M. Eder 4 ), and 

 others. While J. M. Eder 5 ) looks upon silver subhaloid as a 

 molecular compound, M. Carey Lea 6 ), E. Bauer 7 ), L. Gunther 8 ), 

 and Lüppo-Cramer 9 ), consider it an absorption compound of colloidal 

 silver and silver haloid, thus practically maintaining Arago's old 

 silver-germ theory in a new shape. However, it is impossible yet to 

 point out a single fact in photography from which it appears which 

 of these two theories is to be preferred; all chemical reactions on 

 the latent image might be accounted for by either theory and 



!) Compt. rend. 1843: T. 16; Nr. 25. 

 T. 17; Nr. 4. 

 J. M. Eder. Handb. d. Phot. 1898; Bd. II; S. 111. 



2 ) Americ. Journ. of Science. 1887; Vol. 33; p. 349. 

 Phot. Korresp. 1887; S. 287, 344 u. 371. 



3) Zeitschr. f. phys. Chemie 1905; Bd. 54; S. 305. 

 Chem. Gentralbl. 1906; Bd. I; S. 807. 



J. M. Eder. Jahrb. f. Phot. u. Repr. 1906; S. 473. 



4 ) Sitzungsber. d kaiserl. Akad. d Wiss. zu Wien. Malbtm.-naturvv. Klasse. 

 Bd. GXIV; Abt. Ha; Juli 1905. 



Zeitschr. f. wiss. Phot. 1905; Bd. Ill; S. 329. 



J. M. Eder. Handb d. Phot. 1906; Bd. I; T. 2; S. 277. 



Phot. Korresp. 1905; S. 425 u. 476. 



1906; S. 81, 134, 181 u. 231. 



1907; S. 79. 



5 ) See note 4. 



6) See note 2. 



7) Zeitschr. f. phys. Chemie. Bd. 45; S. 618. 



8) Abhand. d. naturk. Ges. Nürnberg. 1904; Bd. 15; S. 26. 



9) Phot. Korresp. 1906 u. 1907. 



Lijppo Cramer. Photogr. Probleme. 1907 ; S. 193. 



