1895.] A. Pedler — Bleaching action of light on colouring matters. 141 



of any germs floating in the air at the time of preparation, and they 

 were plaeed (a) one set in direct sunlight, (b) one in diffused day- 

 light opposite a 'window with a north aspect, and (c) one set in perfect 

 darkness. Fifteen experiments of this kind were started. 



B. A set of solutions was taken as in A, except that the tubes 

 containing the solution were thoroughly boiled for from 15 to 20 

 minutes in order to kill any germs likely to produce any action. "While 

 the solutions were still boiling the tubes containing them were plugged 

 well with cotton-wool. Sets of these tubes were also exposed in parallel 

 series (a) in direct sunlight, (b) in diffused daylight, and (c) in dark- 

 ness. Eighteen experiments of this class were started. 



C. Sets of the solutions were placed in tubes drawn out at one 

 end and connected with the Sprengel mercurial pump. The solutions 

 were boiled for 15 to 20 minutes, so as to free them from all dissolved 

 oxygen and from all living germs, etc., and they were then completely 

 exhausted of air and hermetically sealed. Sets of the solutions in 

 these tubes were exposed (a) in full direct sunlight, (6) in diffused 

 daylight opposite a north window, and (c) in total darkness. Eighteen 

 experiments of this class also were started. 



D. Specimens of cotton-wool, dyed with solutions of the six 

 colours and then thoroughly dried at 100° C, were placed in test tubes, 

 plugged at their mouths with cotton-wool, and then while thus freely 

 exposed to air in its ordinary hygrometric condition, they were placed 

 (a) in direct sunlight, and (b) in total darkness. Twelve experiments 

 of this class were started. 



E. Sets of dyed cotton-wool dried at 100° 0, were placed in tubes 

 rendered vacuous by the Sprengel pump, and then hermetically sealed 

 and exposed (a) to direct sunlight, and (6) in total darkness. Twelve 

 experiments of this class were started. 



F. Specimens of asbestus were freed from organic matter and 

 from any organisms, etc., by ignition, and dyed with the colours and 

 carefully dried at 100° C. Specimens were placed in test tubes freely 

 exposed to the air in its ordinary hygrometric state, and plugged with 

 cotton-wool only. These were placed one set (a) in full direct sunlight, 

 and (b) in total darkness. Ten experiments of this class were started. 



G- Similar sets of asbestus specimens dyed with the colours and 

 dried, were placed in tubes carefully exhausted by the Sprengel pump 

 and hermetically sealed. One set was placed (a) in full direct sun- 

 light, and a second set (b) in total darkness. Twelve experiments of 

 this class were started. 



The above sets of experiments wei*e allowed to continue for periods 

 varying in some cases up to nearly three years. In addition also some 



