(-t ) 



According to the investigations of E. English l ) and J. M. Eder 2 ) 

 there are two images in the case of solarization. This question has 

 not jet been satisfactorily cleared up, and a certain amount of con- 

 fusion prevails as to the distribution of the normal and the polarized 

 copy. 



If the time of exposure, resp. the light intensity is increased, the 

 reducibleness of the silver haloid increases in depth, finally to such 

 a degree that provided the time of development be sufficient, the 

 reduction extends to the glass, as is shown by the excellent micros- 

 copic preparations of W. Scheffer 8 ). If solarization sets in, it will 

 first occur in the apparently most sensitive layers, i. e. those at the 

 free surface; consequently the reducibleness decreases from there, and 

 on the time of exposure, resp. the intensity of the light being increased, 

 it constantly extends further down. Thus an image is obtained as is 

 graphically shown by fig. 4, from which it is at once apparent that 

 the solarized image is a normal copy and a surface image. Under 

 this image there is a polarized copy of greater density with AB for 

 its base and from there to the glass there is a strip of fog, the den- 

 sity of which depends on the thickness of the emulsion. 



That after all, in the case of solarization, the copy appears polar- 

 ized, is therefore owing to the normal copy being of less density 

 than the polarized one. It will, however, more or less reduce the 

 contrasts and the wealth of detail. It is consequently contrary to f act 

 to understand polarization by solarization, as is always done. 



(In the figure the section of the solarized image is indicated by 

 finer granulation, which is meant to show that the density has been 

 reduced in that portion). 



This at once accounts for the phenomenon occurring in the case 

 of solarization of silver iodide gelatine discovered by Lüppo-Cramer 4 ) 



i) Phys. Zeilschr. 1900; Bd. 2; S. 62. 

 J. M. Eder, Jahrb. f. Phot. u. Repr. 1902; S. 79. 

 Archiv. f. wiss. Phot. 1900; Bd. II; S. 260. 



2) Zeitschr. f. wiss. Phot. 1905; Bd. II; S. 340. 



J. M. Eder, Handb. d. Phot. 1906; Bd. I; T. 2; S. 287. 



Sitzungsber. d. Kaiserl. Akad. d. Wiss. zu Wien. Mathem-Naturw. Klasse ; Bd. 



GXIV; Abt. Ha; Juli 1905. 



3) J. M. Eder, Jahrb. f. Phot. u. Repr. 1907; S. 31. 



4 ) I cannot omit quoting this experiment, which so clearly confirms the above : 

 "Eine auffallende Erscheinung beobachtete ich endlicb noch bei einem Solarisie- 



* rungsversuch mit Jodsilbergelatine. Unter einem Negativ ergaben die Platten in 

 "drei Sekunden bei diffusem Tageslicht ein ausexponiertes Bild. Eine sechs Stunden 

 "lang unter demselben Negativ belicbtete Platte schien sich in Amidolpottasche, 

 "in welcber sie neben der drei Sekunden belichteten Platte entwickelt wurde, zuerst 



