282 Prof. Rutherford and Mr. Royds on the Nature 



The experimental arrangement is clearly seen in the figure 

 The equilibrium quantity of emanation from about 140 milli- 

 grams of radium was purified and compressed by means of a 



mercury-column into a fine glass tube A about 1*5 cms. long. 

 This fine tube, which was sealed on a larger capillary tube B, 

 was sufficiently thin to allow the a particles from the emana- 

 tion and its products to escape, but sufficiently strong to 



