98 Dr. H. Morton on the Fluorescent Relations of certain 



into it from above, long trails of light running through the so- 

 lution, as shown in fig. 10. 



Fig. 10. 



These trails are variously coloured as follows : a is very faint 

 and olive-green ; b is very bright and of a vivid green ; c is bright 

 sky-blue; and d is of an indigo tint running into violet towards H. 



The appearance is indeed exceedingly beautiful, from the rich- 

 ness of the colours and the delicate manner in which they fade 

 off and blend. 



The brightest bands or trails {b and c) are each penetrated, as 

 it were, from the further side of the tank by a long blade of 

 darkness, the result undoubtedly of the absorptive action of the 

 fluid for the corresponding rays, which causes them to be more 

 rapidly exhausted ; while those at either side, being less energe- 

 tically active and acted upon, penetrate further before their mo- 

 tion is converted into fluorescence. Near H, where the actions 

 of absorption and fluorescence are most intense, the light hardly 

 seems to pass beyond the actual surface of the liquid. 



Exact parallels to all these actions were observed by Stokes 

 in chlorophyl (Phil. Trans. 1852, Part II. p. 489) ; but though I 

 have examined all the substances enumerated by him, I have in 

 no case found so beautiful an exhibition of the phenomena as 

 this solution furnishes. 



When the light from these trails is examined with a hand- 

 spectroscope, it is seen that the bright green one b wants the 



