38 Br. R. D. Thomson on the History [Jan. 



so long have been considered as ascertained. So little at- 

 tention, however, it appears had been paid to the subject 

 by mineralogists, that Lucas in his Tableau Methodique 

 des especes Minerales, published in 1813, places the Zimapan 

 mineral under phosphate of lead, and even in 1817, Brei- 

 thaupt committed the same mistake.* After the analysis 

 of Des Costils this interesting mineral remained in com- 

 parative oblivion till April 1830, when Professor Sefstrbm, 

 while examining iron from the Mine of Taberg in Smaland, 

 introduced a new substance to the acquaintance of chemists, 

 by the discovery of Vanadium, f 



In the begining of 1831, Wohler appears to have sub- 

 jected the brown lead mineral from Zimapan to analysis, 

 and to have concluded that it was a compound of vanadic 

 acid, and protoxide of lead. J 



In the course of the winter 1830-31, Mr. Johnston states 

 that his attention was directed to a mineral from Wanlock- 

 head, which he obtained from a mineral dealer as an arse- 

 niate of lead, and that he procured by analysis, what at 

 first he considered impure oxide of chromium ; but having 

 repeatedly attempted to separate the chromium in an insu- 

 lated state, and several properties appearing which were 

 distinct from those of chromium, he concluded that it was 

 a new substance. § 



Having finished the history of the discovery of the vana- 

 diate of lead so far as I am acquainted with it, I proceed 

 now to the consideration of the properties and composition 

 of such specimens as have been subjected to examination. 



1. The only quantitative analysis of the native vanadiate 

 of lead which has hitherto been published, is that of Berze- 

 lius. The specimen examined was from Zimapan, and pos- 

 sessed little colour, but it was mixed with oxide of iron, 

 which gave it a brown appearance. || Nothing is said of its 

 density, but Breithaupt under the title of Vanadiner blei 

 spath, states the specific gravity of the Zimapan mineral at 

 6*831 .H The process of the Swedish chemist was to dissolve 



* Del Rio's Letter to Gilbert, 1. Annalen der Physik und de> physikalischen 

 chemie, lxxi. 7. 



t Ann. de chim. lvi. 105. 

 $ Ann. de chim. xlvi. 111. 

 § Edinburgh Journal of Science, v. 166. 



|| Kongl. Vetenskap. Acad. Handl. 1831. Annal de Chim. xlvii. 402. 

 % Vollstandig characteristik des Mineral Systems, 54 — 1832, 8vo. 



