Vol. 56.] OF MINERALS CONTAINING EARE ELEMENTS. 525 



gained as far from proportionate to the work devoted for many years, 

 nay for generations, by numerous investigators to the separation of 

 these earths. We are evidently confronted here by one of the most 

 difficult problems of experimental chemistry. Probably, however, 

 we have here a clue to important information concerning one of the 

 fundamental tenets of modern chemistry : the doctrine that all matter 

 is composed of a certain number of simple and intransmutable 

 substances, — a doctrine not easily acceptable by the philosopher, 

 yet, as it would seem, more firmly founded on innumerable experi- 

 ments than any other scientific hypothesis. 



Closely allied in several respects to the earths contained in gado- 

 linite is the oxide of another element, discovered by Berzelius in 

 1829 and described by him in the Transactions of the Royal Swedish 

 Academy of Sciences under the name of thorium. He found it 

 in a black gadolinite-like mineral sent to him by the Rev. M. Thrane 

 Esmark. The mineral occurred very sparingly in the zircon- 

 syenite district on Langesund Fjord in Norway : this is one of the 

 richest-known localities in distinct mineral-species. Its only rivals 

 in this respect are the iron- and manganese-mines in the ore-field of 

 Philipstad, the volcanic region of Vesuvius, and the neighbourhood 

 of Kangerdluarsuk Fjord in Greenland. The Norwegian locality, 

 often, though less correctly, called Brevig in mineralogical litera- 

 ture, was discovered at the beginning of the nineteenth century by 

 J. Esmark. Since that time it has been visited by numerous 

 Norwegian and foreign mineralogists ; aid a few years ago Prof. 

 W. C. Brogger published an excellent mineralogical description of 

 the locality. 



Thoria is distinguished by its weight, which approaches that of 

 lead, and by several chemically remarkable reactions, which were 

 admirably made out by Berzelius, though he had only a few 

 grammes of the new mineral at his disposal. For a long time 

 thorium remained one of the rarest of elements, though it was soon 

 met with as a subordinate constituent in a number of other minerals. 

 Thus in 1839 Karsten, Professor at the Mining Academy of Frei- 

 berg, found that thorium enters into the composition of a mineral 

 discovered a few years before in the Ilmen Mountains (Ural), to 

 which the name monazite, from fiopd£eiv, to be alone or rare, 

 had been given. Karsten's statement was doubted by many chemists,, 

 but confirmed by Berzelius. Furthermore, thorium was found, 

 though only in small percentages, in pyrochlore from Brevig by 

 Wohler ; in euxenite from Arendal by Mosander and Chydenius ; in 

 gadolinite, mixed with orthite, from Ytterby by A. J. Wimmerstedt : 

 and in a brown, altered variety of orthite (called v a site) from 

 Ronnsholmen near Vaxholm by Fr. Bahr. 



As recently, however, as about 1870 the thorite from Brevig (or the 

 variety of it which was called orangite) was the only mineral that 

 yielded the raw material necessary for obtaining even a few grammes 

 of thoria. To procure a few hundred grammes of this earth would 

 at that time have been considered by every chemist as quite impos- 



Q. J. G. S. No. 223. 2 n 



