216 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1947 



three transuranium elements, where it was possible to graduate from 

 tracer scale investigations to the more certain investigations with the 

 pure elements, it does not seem too optimistic to hope that this will 

 soon also be true for curium. 



It is, of course, not improbable that it will eventually be possible to 

 prepare isotopes of curium of longer half-life. It is, in fact, even 

 probable that isotopes such as Cm^^^, Cm^**, Cm^*^, or Cm^*^ may have 

 longer half -lives and that these isotopes may eventually become avail- 

 able for investigation. 



