PENETRATION OF X-RAYS. 



77 



TABLE 47. Penetration of rays and reversal of tube; 5^ = 25 cm. Exposure about 

 3 sec. prior to condensation without cutting off the radiation; air, s 1.2; wood 

 fog chamber not cased (fig. 41). 



* Second exhaustion made, but not recorded. 



f Initial low datum. 



i Galvanoscope discharged at 6 meters and through lead plate, but much more slowly 

 than the instant collapse at 6 cm. 



First plate filters out the axial rays. The remainder have no observable effect, and 

 are virtually transparent. Coronas clear and multi-annular apart from rain. 



If Second exhaustion necessary to avoid periodicity. 



**Note the reduction of A^at 600 for i plate, which does not occur at Z? = 6 cm. 

 and D = 200 cm. 



