528 BARON A. E. NORDENSKIOLD ON THE OCCURRENCE [Aug. I9OCV 



an observation subsequently confirmed by Berzelius, who, to his 

 astonishment, found this to be the case even with the most compact 

 magnetite from Dannemora. 



As I have already stated, cleveite was the first terrestrial mineral 

 in which helium was shown to be present. The occurrence of this 

 gas has since been proved in a number of other minerals containing 

 rare earths : that wherein it has been found in the greatest 

 quantity being fergusonite, which in all other respects has a 

 composition quite different from the composition of cleveite, since in 

 fergusonite the rare earths are combined with tantalic and niobic 

 acids. The history of the discovery of this mineral and of the rare 

 metallic acids which it contains also presents interesting and instruc- 

 tive features which cannot be passed over even in so brief a sketch 

 as the present. 



Tantalic acid was discovered in 1802 by Anders Gustaf Ekeberg, 

 Professor of Chemistry at the University of Upsala, in a black 

 mineral, resembling iron-ore, from Skagbole in the parish of Kimitto 

 (Finland). This mineral had attracted attention by its high specific 

 gravity, which is 7 or 8 times that of water. It had been already 

 casually mentioned in a dissertation ' On the Nature of Tin & its 

 Ores,' published in 1772 at the University of Abo by August 

 Xordenskiold. On closer examination Ekeberg discovered that the 

 supposed tin-ore contained the acid of a new element, tantalum, 

 and. the mineral was named tantalite. It has since then been 

 found at other localities, but always in small quantity : as, for 

 example, by Berzelius in the neighbourhood of Falun, and by Nils 

 Nordenskiold in the parish of Tammela (Finland). In the same year 

 as that in which Ekeberg published his treatise on tantalic acid r 

 Charles Hatchett described in the Philosophical Transactions of the 

 Royal Society an element closely related to tantalum, which he 

 called columbium, a name that has since been supplanted by 

 niobium. Ekeberg subsequently found that tantalic acid also 

 enters into the composition of a mineral from Ytterby, which was 

 named yttrotantalite. 



A new locality for these minerals, or others allied to them, was 

 discovered in the first decade of the nineteenth century by Karl 

 Ludwig Giesecke. This remarkable man, who began life as an 

 actor and playwright, devoted himself zealously to the study of 

 mineralogy, obtained or assumed the title of a Prussian Bergrath, 

 went to Copenhagen, and was entrusted by the great Fasroe and 

 Greenland Companies with the mineralogical exploration of those 

 outlying dominions of the Danish crown. He dwelt for a long time 

 in Greenland, travelled by boat with the natives along its western 

 coast, and long after his departure his memory was cherished by 

 the officials of the Company as well as by the childlike and simple- 

 minded natives. After his return, he was invited to come to Scot- 

 land to give an account of his discoveries and the localities of the 

 minerals which he had collected in Greenland and sent home. 

 During the Napoleonic wars these collections had been confiscated 

 by British men-of-war and sold by auction. In this way they had 



