146 THE NEW KNOWLEDGE. 



to the argon family of the elements in the periodic law, 

 This dazes the old gentleman a little, but he returns to the 

 attack. "This so-called emanation is probably nothing but 

 dust in the air which has beccme radio-active through con- 

 tact with the thorium. You, know that the international ' 

 congress of chemists has decided that a new element, to 

 have any validity, must have a mapped spectrum. I am 

 going to ask you, then, for the spectrum of this emanation 

 which you tell me is a transmuted element from thorium." 

 This request is hardly fair, for the instruments which meas- 

 ure the properties of these interesting bodies, the electro- 

 scope and electrometer, are hundreds of thousands of times 

 more refined than the most delicate spectroscope. 



Yet we are able to satisfy him; not, it is true, with the 

 emanation from thorium, for its life is too short. Half of it 

 has died in a minute from the time of its birth, and this is too 

 short a time for the adequate observation of the infinitesi- 

 mally small quantity of matter involved. 



But we can easily satisfy him with a perfectly similar 

 emanation from the new element radium ; for the life of the 

 radium emanation is longer. 



About the first of June, 1904, Sir William Ramsay suc- 

 ceeded in determining with certainty the position of certain 

 lines in the spectrum of this transmuted element, the " em- 

 anation" evolved from radium. 



The spectral lines characteristic of the emanation are 

 transient because the element itself is transient, but they 

 are definite, and different from the lines belonging to the 

 spectrum of any other known form of matter. 



It is interesting to note in this connection that one of the 

 most persistent of the lines observed is identical with one 

 observed in a lightning flash by Pickering. So sure is Ram- 

 say that the emanation from radium has a definite though 



