a particles from Thorium and Actinium Products. 651 



are all compared with the range of: thorium C 2 as standard 

 (8*60 cm. at 15° C). The ranges are tabulated in the table 

 at the end of the paper, and are in fair agreement with the 

 figures given by Hahn * and by Barratt f. The range of 

 thorium X, which has not been determined before, was found 

 to be 4-30 cm. at 15° C. 



Fiff. 3. 



Curve I.: 



II. 



III. 



IV. 



I 2 3 4 5 6 



ft/iNGE OFOL PARTICLES IN CMS. 



a particles from Act X, Act C, Act Em, Act A. 

 „ „ Act X, Act C/'Act Em. 

 ,, „ Act X, Act C. 

 Act X. 



Similar experiments were carried out with actinium X, 

 under exactly the same conditions as described above in the 

 case of thorium X. A very thin film of actinium X of 

 sufficient activity was prepared. 



Curve I. of fig. o shows the 



* 0. Halm, Phil. Mag. xii. p. 82 (1906). 



t T. Barratt, Proc. Phys. Soc. xxiv. p. 112 (1912). 



