( 42G ) 



where .<] is tlie widtli ut' the diffractiuu slit currespuiidiug willi a 

 broadening", the values in the following table: 



N". of 

 experiment. 



S] 111 micra. 



A in Angstrom 



units. 



If, and this is nut impossible, these values of .«ii, are enlarged by 

 photographic irradiation, the wave lengths would still become smaller. 

 Though very desirous to be enabled to give the limits of the Rönt- 

 GEN rays with more certainty, we think this an impossibility with 

 the means at our disposal. Not till Rönïgen tubes are produced, 

 remaining in good working condition as long as those we have 

 made use of, but giving out rays of much greater energy, one may 

 succeed to make measurements instead of estimations. 



Physical Laborator i/ 

 University Groningen. 



