174 



Capt. Abney. On the Effect of the [Dec. 15- 



action also extended to that region. The printing action on the grey 

 form (which was submitted to the spectrum in a film of gelatine) is 

 shown in fig\ 26. On comparing these together, it will be seen that 

 the maximum action commences between G and F (nearer F than G) y 

 and that the main difference in their impressed spectra lies in the tails 



gBr + AgN0 3 , on paper 



Print. 



... Print. 



reen AgBr in collodion with Print. 

 or without AgN0 3 . 



Jrange AgBr in collodion Print. 

 gelatine with or without 

 AffNO,. 



rey AgBr in gelatine 



Print. 



gBr on paper washed from Developed 

 AgN0 3 , developed with acid (long 

 or ferrous citro-oxalate de- exposure), 

 veloper. 



itto ditto (short 



exposure). 



rey AgBr in gelatine, deve- Developed 

 loped alkaline or ferrous (long 

 oxalate. exposure). 



itto 



ditto 



(short 

 exposures- 



range AgBr in collodion or Developed 

 gelatine, developed alkaline (long 

 ferrous oxalate or acid de- exposure), 

 veloper. 



itto ditto (short 



exposure). 



reen AgBr in collodion, Developed 

 developed ferrous oxalate. (long 



exposure). 



itto 



ditto 



(short 

 exposure) 



on the least refrangible side. When the colour transmitted by these 

 three forms is taken into account, these differences are to be expected. 

 Whether the silver bromides were exposed with a slight excess of 

 silver nitrate, or with a slight excess of soluble bromide, no difference 

 in the spectra resulted. 



We next come to spectra developed on the different preparations of 



