240 THE ORIGIN OF LIFE 



exposure being equal to that of each of the others 

 separately. 



In every instance the resultant effect in the 

 former was greater than in the latter case. And 

 this is due to the fact that the cube A is more 

 transparent to the light from B — that is the light 

 which it can itself radiate — when it is screened 

 from the spark than when it is itself fluorescing. 

 This result has been tested in many ways, which 

 it would take too much space to describe here. 

 It may, however, be pointed out that this experi- 

 ment alone can be explained on the supposition 

 that the fluorescent rays have the power of dimin- 

 ishing the intensity of the fluorescence just as 

 Becquerel and Stokes found that the less refran- 

 gible rays have the property, when acting simul- 

 taneously with the more refrangible rays, of 

 diminishing the intensity of the phosphorescence 

 in a previously excited screen. It seemed, there- 

 fore, that the fluorescent light might thus help to 

 extinguish itself But this is not so. 



Thus if the two cubes A and B be illuminated 

 by rays perpendicular to the plane of the paper, 

 and the fluorescent light in the direction As be 

 observed, according as the cube A is screened from 

 its neighbour, or exposed to its illumination, there 

 is found to be no appreciable difference in the 

 brightness of A, and if anything there is an 

 increase rather than a diminution, and this slight 

 increase would appear to be merely due to the 

 scattered light from B, as may easily be verified 



