the Origin of Radium. 607 



of thorium and uranium. A clove-brown, translucent 

 specimen. Contained a little lead. 



11. Samarskite. — A niobate and tantalate of cerium and 

 vttrium. Uranium and iron also present in considerable 

 quantities. 



12. Orangite. — A variety o£ thorite. This specimen was 

 a single transparent crystal of a honey-yellow 7 colour. It 

 contained some lead. 



1."). Etusenite. — A niobate and titanate of yttrium, erbium, 

 cerium, and uranium. The sample was of a brownish-black, 

 massive variety. 



14. Thorite. — A silicate of thorium and uranium (ThSi0 4 ) . 

 The sample was of a massive variety, yellowish-brown in 

 colour. It contained a little lead and iron. 



15. Fergusonite, — Essentially a metaniobate (and tantalate) 

 of yttrium with erbium, cerium, uranium, and iron. The 

 -ample was of the variety called " tyrite/' and was not 

 completely soluble in hot, concentrated sulphuric acid. The 

 uranium-radium ratio was therefore calculated on the basis 

 of the portion soluble in the acid. 



lb*. ^Eschf/nite (?). — This specimen was purchased under 

 the name of asschynite, but failed to show the characteristic 

 behaviour of that mineral before the blowpipe. Analysis 

 showed that it was essentially a niobate and titanate of the 

 rare earths, but its further identification was not attempted. 

 In its general appearance it resembled a:\schynite. 



17. Xenotime. — Essentially yttrium phosphate containing 

 erbium and cerium. General formula (I 7 ", Ce,Er).P0. 1 . The 

 sample consisted of a single imperfect crystal. 



18. Monazite. — This substance consists chiefly of cerium 

 phosphate, but also contains notable quantities of lanthanum 

 and didimium. General formula (Ce, La,Di)P0 4 . The 

 sample was in the form of sand and contained about 5 per 

 cent, of thoria. 



U>. Monazite. — The sample consisted of a single, good- 

 sized crystal. The amount of thoria present was from 7 to 

 9 per cent. 



-?<>. Monazite. — This sample was in the form of sand and 

 contained about 5 per cent, of thoria. 



21. Monazite. — A massive variety from Portland, Conn. 

 Stated to contain about <S per cent, of thoria. 



22. Allanite. — A complex silicate, the general composition 

 of which is represented by the formula (Ca,Fe) 2 . (A10H) 

 (Al,Cr,Fe) 2 . (SiO^j. It also contains small quantities of 

 < 'e. La, Di. ami Er. This material was slightly radioactive, 

 but the emanation which it contained corresponded to only 



