PENETRATION OF X-RAYS. 



75 



59. Electrical effect for different distances. To roughly estimate the 

 state of the room iu relation to the ionizing effects of the X-rays, the 

 time of collapse of the gold leaves was taken, when the galvanoscope 

 standing on an earthed brass plate was covered with a glass bell jar. 

 Table 46 needs no explanation. In the second part of the table the 

 time of collapse decreases about as the square of the distance and is 

 thus quite different from the fog-chamber effect. At short distances 

 the galvanoscope registers a sudden throw when the circuit through 

 the X-ray tube is first made. The effect of this throw is the same as 

 if negative electricity entered the metal frame of the electroscope, and 

 it is therefore probably electrostatic induction on the brass foot plate 

 coming from the cathodal conductor. 



TABLE 46. Electrical effects of X-rays. Galvanoscope in glass bell jar, walls 0.5 cm. 



thick. 



* Positive and negative charges behave alike. 



60. Apparent penetration of the X-rays coming: from 600 cm The 



astonishingly small distance effect observed made it seem probable 

 that the effective rays are of a penetrating kind. Table 47 (to be inter- 

 preted later) apparently bears this out, though in reality it merely 

 separates the axial and lateral radiations. Advantage is taken of the 

 sufficiency of short exposures whereby the tube is kept more constant. 

 The apparatus is shown in figure 41, where A is the fog chamber and 

 P the plates. 



To take first the experiments in table 47, when the distance between 

 the lead screen at the fog chamber and the X-ray bulb is D -- 600 cm. , 

 which are smoothest (curve 79), it appears that a single lead plate 0.14 



