( 5) 



and which points to the very rapid decrease in redncibleness of 

 silver iodide when solarized. 



II. A few phenomena occurring with polarization accounted for 

 by considering the form of the image. 



From the form of the image in lig. 4 it appears how impregnation 

 of the silver-haloid gelatine plate with bichromate before exposure 

 may influence the result obtained, which was pointed out by Bolas l ). 

 J. M. Eder and G. Pizzighelli s ) attributed the result exclusively 

 to hardening of the gelatine, by which development in the normal 

 image is disturbed, and in which solarization acts hardly any part. 

 It is evident that this image in the hardened gelatine more or less 

 coalesced with the solarized image, in proportion to the strength 

 of the bichromate solution employed, by which the development of 

 the latter is suppressed to a greater extent and the polarized copy 

 appears richer in contrast and detail. The fog, however, is not done 

 away with. 



While in the case of normal copies the latter may be removed 

 with Farmer's reducer 3 ), this treatment does not succeed in the case 

 of polarization. The slight diffusion of this reducer discovered by 

 W. Scheffer 4 ), by which the action slowly progresses downwards 

 from layer to layer, at once accounts for this phenomenon. 



Of more significance to our knowledge of the latent image is the 

 so-called neutralization of solarization by retarded development. That 

 the said phenomenon is regarded as such is only attributable to the 

 ideas of solarization and of polarization being confounded. 



Development is retarded either by decreasing the amount of alkali 



"gar nicht zu reduzieren, wahrend das kurz exponierte schon in alien Einzelheiten 

 "erschienen war. Nach einiger Zeit merkt man indes, dass auch auf der überbe- 

 "lichteten Plalte ein Bild vorhandcn ist ; dasselbe sitzt nur in den tie f eren Schichten 

 "allerdings als normales Diapositiv, d. h. noch nicht solarisiert wahrend in der 

 "Aufsicht erst nach langerer Entwicklung etwas zu sehen ist. Beim Fixieren merkt 

 "man deutlich, dass in der obersten Schicht der lange belichteten Platte kein Bild 

 "vorhanden ist, inlem nach kurzem Fixieren das Bild auch in der Aufsicht kraf- 

 " tiger wird, offenbar weil das unreduzierte Jodsilber der obersten Schicht wcgge- 

 «nommen wird". (J. M. Eder, Jahrb. f. Phot. u. Repr. 1903; S. 46. Zeitschr. f. 

 wiss. Phot. 1903; Bd. I; S. 17). 



i) J. M. Eder. Handb. d. Phot. 1902; Bd. Ill; S. 115. 

 Phot. News. 1880; Vol. 24; p. 304. 



2 ) J. M. Eder. Handb. d. Phot. 1902. Bd. Ill; S. 115. 



8) J. M. Eder. Handb. d. Phot. 1902 Bd. Ill; S. 555. 



4 ) Brit. Journ, of Phot. 1906; p. 964. 



J. M. Eder. Jahrb.' f. Phot. u. Repr. 1907; S. 26. 



