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 placed (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, (h) 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, (b) 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 (6) in total darkness. Twelve experiments 
of this class were started. 
E. Sets of dyed cotton-wool dried at 100° C, were placed in tubes 
rendered vacuous by the Sprengel pump, and then hermetically sealed 
and exposed ( a ) to direct sunlight, and ( b ) 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 were allowed to continue for periods 
varying in some cases up to nearly three years. In addition also some 
