422 Messrs. Nichols and Snow on the Influence of 



indications of absorption between '5/ju and *6^. At high 

 temperatures this absorption in the yellow disappears, and we 

 see the gradual development of a maximum in the red. The 

 case is of interest in that it is the only one in which reflecting- 

 power at high temperatures exceeds that at lower temperatures 

 for any considerable portion of the visible spectrum. The 

 spectrum shown in fig. 14 is characteristic for zinc oxide at 

 25°, the same curves being obtained whenever a film was 

 measured. The curves for high temperatures, however, were 

 found to be ' applicable only to a single film, the variations 

 being due to causes which we were not in a position to con- 

 trol. Another typical form is shown in fig. 15, in which the 

 carve for 600° is that which characterizes a simple sulphur- 

 yellow (compare with fig. 4). The curve for the cold film 



Fig. 15. 



6 - 



*■- 



2 - 









Zu 



lOM) 



- v x 











- 









2S m 



- 









6oo* 



\ 





lr 



f/~ 



p*- 



\ 













1 



8 C 



£ F C~ 



in this case, however, differs in no essential from that which 

 had been obtained from the film to which the previous figure 

 pertains. 



