( 2 ) 



Physics. 'A contribution to our knowledge of the solarization 



phenomenon and of some other properties of the latent image". 

 By A. P. H. Trivelli. (Communicated by Prof. S. Hoogewerff). 



(Communicated in the Meeting of March 28, 1908). 



I. The image. 



In order to enquire into the density gradation a photographic 



plate may be exposed in two ways: 



a. with constant light intensity and varying time of exposure; 



b. by equal exposures, with different light intensities. 



In order to eliminate the possibility of other circumstances being 

 different, particularly those under which development is carried out, 

 the first method lias been adopted, a plate being divided into strips, 

 and each succeeding strip receiving a longer exposure than ihe 

 preceding one- This is combining several trial plates into one. In 

 my opinion an "image" cannot be said to appear in this case; it 

 only appears if the second method is adopted. 



The results obtained by equal exposures with different light inten- 

 sities I will call copies. A copy always shows an image, which may 

 be positive or negative. 



By a normal or non-polarized copy I understand copying positive- 

 negative-positive- etc., which may be represented by 



± -> =F 

 By a polarized copy I understand copying positive-positive-etc. or 

 negative-negative- etc., which may be represented by 



=b -> ± 

 According to the investigations of Warnerke '), W. Abney 2 ), 

 K. Schaum and V. Bellach s ), R. Neuhaus 4 ), and W. Scheffer 5 ), 

 the differences in density which appear in a photographic plate 

 after exposure and development, may be ascribed to differences in 

 the depth of the reduced silver haloid. So the image must have a 



i) Phot. Archiv. 1881; S. 85 u. 119. 

 Phot. Mitt. Bd. 18; S. 65, 98 u. 235. 

 J. M. Eder, Handb d. Phot. 1902; Bd. Ill; S. 106 u. 108. 



2) J. M. Eder, Hand. d. Phot. 1902; Bd. Ill; S. 102. 



3) Phys. Zeitsch. 1902; Bd. IV; S. 4. 



J. M. Eder, Handb. d. Phot. 1903; Bd. Ill; S. 819. 

 4; Wied. Annal. d. Phys. u. Ghem. 1898; Bd. 65; S. 164. 

 5) Phot. Glnonik. 1904; S. 366. 



Phot. Bundschau. 1904; S. 121. 



