88 



VAPOR NUCLEI AND IONS. 



Table 34. Revision of distance effects. Large wood fog chamber. 20 x 12X55 



cm. Exhaustion during exposure. 



Terminal corona; same for 7 and 9 cells. 



theory of the phenomena; but the equations n = n /(A -\-D) 2 and n = 

 n /(A-{-D), where A is constant and D the distance between bulb and 

 fog chamber, may be adduced to accentuate the order of values observed. 

 This has been done in case of table 32, showing that for the non-incased 

 bulb even the inverse first power of D varies more rapidly than the 

 observed phenomenon. To a much greater extent is this true for the 

 wood fog chambers. The phenomenon itself is clearly a case of super- 

 position of primary and secondary radiation. The latter, moreover, is 

 furnished not only by the environment of the X-ray bulb, as shown in 

 fig- 39 by surrounding the bulb with a windowed lead case, but also by 

 the immediate environment of the fog chamber. The small distance 

 variation encountered would then seem to be explained by supposing 

 that relatively much secondary radiation is released by relatively weak 

 primary radiation, as compared with a case of strong primary radiation. 

 Under all circumstances the total effect is an integral to be extended 

 over the whole surface and possibly the interior of the room. Finally, 

 one should recall that the rate at which ions are produced by the radi- 

 ation must vary as the square of the number observed. 



