( 29) 



with that of silver haloid is also shown in the amount of halation. 

 In fig. 5 the foliage of the tree is affected by it, while the houses 

 round the sky near a do not show any ; there the halation was too 

 slight to exceed the liminal value of the silver haloid. In fig. 6 the 

 dark lead frame of the window also shows the destruction of the 

 germ owing to halation ; on the other hand on the right side it was 

 able to form fresh germs through a more powerful action. 



That the difference in light sensitiveness between the germ and 

 the silver haloid is great, appears from the backs of the dogs, and 

 from the shoulders of the female figure to the right in fig. 5. The 

 narrow white strip indicates that after the germs had been totally 

 destroyed at the free surface, for some time longer the silver haloid 

 again began to supply germs, first in the most strongly exposed 

 portions, and then gradually also in those which received less expo- 

 sure. Consequently if the action of the light increases, these strips 

 must become narrower, which is also shown by the figure, as the 

 dog to the left was more glossy than the one to the right. 



The white strips along the edges of the black objects in the back- 

 ground are of quite a different nature. These are to be ascribed 

 entirely to irradiation, for in the case of stronger light intensities 

 occurring side by side they are broader than where the intensity is 

 less great. 



If observed very closely by light reflected at an angle, these bright 

 strips are seen to possess a greater gloss than the portions immediately 

 adjoining them. To the left of the tree top this is easier to see than 

 to the right. The light from the wall has acted more intensely to 

 the left than to the right, and notwithstanding the polarization a 

 copy of greater density is shown there. That the critical exposure 

 should have been surpassed, is out of the question here. 



This phenomenon, too, can be accounted for according to the theory 

 given, for in this theory it has been stated, that the critical exposure 

 is not surpassed till the secondary exposure has formed a greater 

 amount of a silver subhaloid than is present in consequence of Ihe 

 primary exposure. Consequently after the liminal value of the silver 

 haloid has been surpassed, a new surface image can originate, the 

 density can increase afresh, and still at (he same time the copy 

 will remain polarized. 



All the abnormalities in the figures 5 and 6 have thus been 

 accounted for. 



In conclusion I wish to express my best thanks to Mr. P. H. 

 Eykman for finding materials and placing them at my disposal, 

 and for his constant interest in my work. 



