522 BARON A. E. NORDENSKIOLD ON THE OCCURRENCE [Aug. I9OO, 



have obtained a great systematic importance for chemical science, 

 and also have been practically utilized, as for example (together with 

 thoria) in the solutions with which mantles are impregnated for the 

 production of the Welsbach incandescent light. 



This incandescent light had been observed already by Cronstedt. 

 In his above-mentioned paper he writes, concerning the Bastnas 

 tungsten, as follows : — ' When it is fused with charcoal-powder zinc 

 is seen to burn with its usual name, but in the brass test the copper 

 does not increase in weight.' In order to understand the meaning 

 of this, one must remember that at that time the dazzling white 

 light which zinc emits when burning was regarded as characteristic 

 for zinc-ores, as also the reaction that takes place when copper fused 

 in a crucible with a substance containing zinc is turned into brass 

 and augments in weight. Hence the remark of Cronstedt, which 

 shows that the beautiful incandescent light of the rare earths had 

 been noted already in the middle of the eighteenth century by our 

 observant metallurgists. They had mistaken this light for that 

 which radiates from glowing lana philosophica, and played so 

 mysterious a part in the fancies of the alchemists. 



Among the minerals remarkable in the history of the discovery of 

 the rare earths or acids, the one met with next after Bastnas 

 tungsten is a black, obsidian-like substance from the felspar-quarry 

 at Ytterby, near Stockholm. This mineral is mentioned for the 

 first time under the name of black zeolite in a letter from Bengt 

 Reinhold Geijer, published in Crell's ' Chemische Annalen ' for the 

 year 1788. Six years Q later John Gadolin, then lecturer on chemistry 

 at the University of Abo, published in the Transactions of the Royal 

 Swedish Academy of Sciences a chemical analysis of this mineral, by 

 which he proved that it contained a new earth, different from lime, 

 magnesia, and alumina, from the baryta of Scheele and the strontia of 

 Klaproth, and characterized by its precipitation from acid solutions 

 by oxalic acid. 



Later, in 1797, Yauquelin discovered glucina, in emerald and 

 beryl. The discovery of these new earths was then as unexpected 

 and as important to chemical science as T. A. Arfvedsson's dis- 

 covery of the alkali, lithia, in 1818 ; Berzelius's discovery of the 

 element selenium in 1818 ; and Rayleigh & Ramsay's discovery 

 of new elements in the atmosphere of the earth in our own days. 

 A closer examination of the ' black mineral from Ytterby and the 

 curious earth found therein ' by Anders Gustaf Ekeberg, Professor 

 of Chemistry at Upsala, was published in the Transactions of the 

 Royal Swedish Academy of Sciences in 1797. The new substance was 

 there called ytterjord (=yttria), and the obsidian-like mineral 

 from which it had been obtained, yttersten, a name afterwards 

 changed to gadolinite. 



A number of minerals are now known containing elements of 

 the cerium group, but the mineral (cerite) in which cerium was first 

 discovered has so far been found only at the mines of Bastnas. The 



