456 Proceedings of Royal Society of Edinlurgh. [july 16 , 
Experiment 9. — Blue light (strong). 
High S : Here there is a pinkish bright line through the middle 
of a light blue band. 
- S : The whole band gets dashed with pink. 
- S : The pink seems all to separate out to form edges for 
the whitish-blue band. 
- S : The pink edges become darker red and then reddish- 
brown, and outside all is a zone of blue darker than 
the central band. 
— S means “ diminished speed.” This blue light was not pure, 
a good deal of red coming through the glass. 
Experiment 10. — Blue light (weak). 
Slow S : Central part light blue ; edges dark blue. 
+ S : Whole image homogeneous blue. 
Experiment 11. — Light of an Argand lamp passed through solu- 
tion of CuSO^ in a cylindrical beaker. 
Slow S : Central band bluish-violet ; edges green. 
+ S ; Central part gets yellowish-green, and then green, the 
borders retaining their original green, but being much 
darker than the central band. 
The central part was seen to be of much greater intensity than 
the edges, when the light was viewed in the mirror at rest. The 
changes of colour in this experiment were remarkably decided. 
There was no ambiguity about the green of the final stage. Never- 
theless, the spectroscope showed greater apparent intensity of blue 
and violet in the light than of green. A good deal of yellow got 
through, but not much red. 
Experiment 12. — Same light as in 11, but much feebler. 
Slow S : Image all bluish-violet, but faint. 
-i- S : Whole image greenish. 
Experiment 13. — Sodium light. 
Flame 2| feet from mirror. 
Slow S ; Image yellow, with blurred reddish edges. 
+ S : Central part greenish ; edges still dull red. 
+ Central part reddish-brown. 
Flame 4 feet from mirror. — No difference of colour could be 
seen with different speeds. 
