Rays of Radioactive Substances. 329 



was spread over an area 22 sq. cms., and the ratio o£ the 

 current produced by the a- and /3-rays determined between 

 two parallel plates distant 6*1 cms. apart. 

 It was found that 



Thus 



current due to a-rays _ 19 . 7 

 current due to /3-rays 



Wi _ total number of ions due to a-rays 

 W 2 total number of ions due to /3-ravs 



_ 12-7x6-1 

 ~ 154 

 = '5 approx.. 



since we have previously calculated number of ions pro- 

 duced by the /3-rays is 154 times the number produced for 

 1 cm. distance between the plates*. 

 Now 



E x \iW } 5Xi 5x2740 innn 



E 2 = ^w!^i; = -ir- = 100 ° approx - 



since the value of A, for aluminium = 2740 for the a-rays and 

 A 2 for the /3-rays = 14. 



We therefore see that for uranium about 1/1000 of the total 

 energy radiated is carried off in the form of electrons. The 

 ratio is still smaller for thorium and radium. It thus appears 

 that in the permanent radioactive substances the electrons 

 driven off represent ouly a small fraction of the energy 

 dissipated. 



§ 11. Discussion of Results. 



We have seen that the three well-recognizect radioactive 

 substances, uranium, thorium, and radium, all emit both 

 cleviable and non-deviable rays. In this respect they differ 

 from polonium, which gives out no deviable rays. As 

 Becquerel has pointed out, there is little doubt that polonium 

 (radioactive bismuth) cannot be considered as a permanent 

 radioactive substance, for its radiation steadily diminishes 

 with the time. 



We have shown that uranium gives out more deviable rays 

 than radium or thorium, compared with the amount of non- 

 deviable, but the ratio of the amounts of the two types of rays 

 is of the same order. 



In considering the question of the relation between the a- 

 and /3-rays, the results of the chemical separation are of 



* Phil. Mag. June 1902. 

 Phil. Mag. S. 6. Vol. 4. No. 21. Sept. 1902. Z 



