the Electrical Conduction 'produced by it. 

 fi Radiation. 



117 



Thickness of 

 Aluminium. 



Rate of Leak. 



•005 

 •028 

 •051 

 •09 



1 



•68 

 •48 

 •25 



The rate of leak is taken as unity after the a radiation has 

 been absorbed by passing through ten layers of aluminium 

 foil. The intensity of the radiation diminishes with the 

 thickness of meted traversed according to the ordinary 

 absorption Jaw. It must be remembered that when we are 

 dealing with the ft radiation alone, the rate of leak is in 

 general only a few per cent, of the leak due to the a radiation, 

 so that the investigation of the homogeneity of the /3 radiation 

 cannot be carried out with the same accuracy as for the a, 

 radiation. As far, however, as the experiments have gone, 

 the results seem to point to the conclusion that the /3 radiation 

 is approximately homogeneous, although it is possible that 

 other types of radiation of either small intensity or very 

 great penetrating power may be present. 



§ 5. Radiation emitted by different Compounds of Uranium. 



All the compounds of uranium examined gave out the two 

 types of radiation, and the penetrating power of the radiation 

 for both the a and /3 radiations is the same for all the compounds. 



The table (p. 118) shows the results obtained for some of 

 the uranium compounds. 



Fig. 2 shows graphically some of the results obtained for 

 the various uranium compounds. The ordinates represent 

 rates of leak, and the abscissas thicknesses of aluminium 

 through which the radiation has passed. 



The different compounds of uranium gave different rates 

 of leak, but, for convenience of comparison, the rate of leak 

 due to the uncovered salt is taken as unity. 



It will be seen that the rate of decrease is approximately 

 the same for the first layer of metal, and that the rate of 

 decrease becomes much slower after four thicknesses of foil. 



The rate of leak due to the /3 radiation is a different 

 proportion of the total amount in each case. The uranium 



