240 Intelligence and Miscellaneous Articles. 



acknowledge my obligations to M. Delafontaine for the numerous 

 suggest ions with which he has kindly aided my investigations. 



Towards the end of 1876 I was engaged in the miueralogical and 

 chemical study of the American minerals containing niobic acid, and, 

 among others, of samarskite, a considerable quantity of which had 

 been found in North Carolina. In so doing I discovered two new 

 minerals, a report on which was addressed to this Academy. In 

 separating the earths from the samarskite I gained the conviction 

 that they contained no acid oxide of cerium, or at the most only 

 slight traces — a fact which is recorded in the publication of my 

 results*. Other chemists who examined this samarskite (as Mr. 

 Hunt, Mr. Allen, and Miss Swallow) concurred with each other in 

 finding in it some oxide of cerium ; M. Delafontaine, in a private 

 letter dated 4th May 1877, writes to me, " I have ascertained no- 

 thing that can make me doubt the presence of cerium •" and in a 

 letter of the 21st of the same month he passes in review the causes 

 which might have misled me in my conclusions, ending with these 

 words : — " But I suppose you have an equally good method : and 

 we may expect to receive from you a monograph upon a new ele- 

 ment — which, I avow, would give me great pleasure ; for it has 

 already seemed to me that the hypothesis of the existence of such 

 an element would give a satisfactory explanation of certain incon- 

 gruities in the properties of the other earths." In a still more recent 

 letter he says, in regard to the samarskite earths, " I am convinced 

 now of the absence, almost if not absolutely total, of the oxide of 

 cerium ; and no one has any longer a doubt on this point." 



M. Delafontaine, to whom I remitted a little of the earth, which 

 I had purified as much as it was then possible for me to do so, and 

 also a large quantity of the mineral, concluded that it was either 

 terbia or a new earth. Not finding, however, the chemical proper- 

 ties correspond to those then known of terbia, I addressed a report 

 to the Paris Academy of Sciences, insisting on my first conclusions, 

 asserting that the new earth is distinguished from, that of the yttria 

 group by the action of sulphate of potasst, from the oxide of cerium 

 by its solubility in extremely dilute nitric acid and in a solution of 

 alkalies supersaturated with chlorine, from lanthanum by the colour 

 of its oxide and of its salts, from didymium by the absorption-lines 

 of the latter in the bright part of the spectrum. I abstained from 

 giving any definite name to the metal constituting the base of this 

 earth, because I knew it was necessary to proceed with great cir- 

 cumspection, working, as I did, amoug a group of oxides which 

 figure among the elements as the asteroids among the planets. But 

 the spectroscope, in the skilful hand of M. Soret, has supplied what 

 was wanting ; and I seize this opportunity of announcing that the 

 existence of the element, which I suspected in 1876, is no longer 

 hypothetical, but real. — Comjptes Rendus cle VAcademie des Sciences, 

 July 22,1878, tome lxxxvii. pp. 148-151. 



* Archives des Sciences Physiques et Ncdurelles, March 1878, p. 283. 



t Being precipitated by a concentrated solution of that salt in the pre- 

 sence of crystals of the same salt, especially when heated, but less readily 

 than the oxides of cerium, lanthanum, and didymium. 



