the Origin of Radium. 613 



uranophane which were used in the investigation described in 

 this paper had been taken from the earth within the last twelve 

 months, and had undoubtedly been subjected to the action of 

 percolating water until their removal. No deficit in the 

 quantity of radium present in these minerals could be detected. 



Soddy has described * an experiment undertaken to 

 determine whether radium is formed directly from uranium, 

 and the results which he obtained have led him to conclude 

 that such is not the case. Similar experiments covering a 

 period of seven months have been carried out by the writer and 

 point to the same conclusion. It is therefore highly probable, 

 as suggested by Rutherford f, that one or more intermediate 

 changes exist between the uranium atom and the radium 

 atom, although the identity of these intermediate products 

 has not vet been established. The suggestion by Rutherford 

 that actinium may be such a substance is of interest since 

 the position of actinium in the family of radioactive elements 

 has not vet been determined. Thorium appears to be quite 

 out of the question because of the total lack of proportion- 

 ality between it and the other substances. 



The persistent appearance of lead as a constituent of 

 uranium-radium minerals may indicate that this element is 

 one of the final (inactive) products of the disintegration of 

 uranium. Quite appreciable quantities of lead were found 

 nt in all of the minerals which were tested for this 

 element (Nos. 1 to 12 and No. 14), with the exception of 

 No. 5, which contained only a very slight trace of elements 

 precipitated in acid solution by hydrogen sulphide. This 

 mineral, No. 5, represents from a geological standpoint the 

 youngest of the compounds examined, and the practical 

 absence of lead from it is only what might be expected if 

 lead were one of the final products. The presence of lead 

 in the secondary pitchblendes from Saxony, Colorado, and 

 Joachimsthal is in itself of little significance, as it is well 

 known that these minerals occur in conjunction with galena 

 and other lead compounds, but the North Carolina uranium 

 minerals are found in a formation (pegmatitic dike) in which 

 no true lead minerals have been identified. The same is true 

 of thorite, which is moreover a well crystallized mineral. 



The writer is indebted to Prof. S. L. Penfleld of Yale 

 University, Mr. Joseph Pratt of Chapel Hill, North Carolina, 

 and Mr. II. 8. Miner, Chemist of the AVelsbach Light Co., 

 tor a number of the minerals used in this investigation. 



L38 Omnge St.. New Haven, Conn., U.S.A. 

 January 28, L905. 



• Nature, May 19, 1904. 



T Bakerian Lecture, Roy. Soc. Lond. 1004. 



