Chemical Science. 189 



and by management has obtained larger crystals of oxide of iron 

 than are usually procured. These crystals are finer the longer the 

 action of the iron and steam has been continued ; they have occa- 

 sionally been obtained one-tenth of an inch in size upon large wire 

 or plates of iron. The crystals are very brilliant, and, under the 

 microscope, perfectly resemble those from Elba or Framont. They 

 are usually rhomboids, covering each other as in the iron ores from 

 those countries, have the same brilliancy and colours, and every 

 other character except size. 



M. Haldat then endeavoured to obtain crystallized oxide of zinc 

 by similar means ; and by using precautions relative to the applica- 

 tion of heat, rendered necessary by the greater fusibility of zinc, 

 succeeded in his object. The oxide had two forms, being sometimes 

 in amorphous globules, and at others in plates covered with rhom- 

 boidal transparent crystals, having the colour of honey. 



As in volcanoes, most of the circumstances meet necessarily in 

 these experiments to produce crystals, it is probable that all the vari- 

 eties of crystallized oxide of iron there found, result from a process 

 analogous to the present *. 



Mr. Daniell obtained very fine octohedral crystals of oxide of iron 

 upon the bars of iron, used in his pyrometrical experiments, and 

 which had been heated with very imperfect access of air f. 



14. DISCOVERY OP VANADIUM IN SCOTLAND. 



Mr. James F. W. Johnston has discovered Vanadium in Scotland, 

 in a mineral from Wanlockhead, resembling in appearance an ar- 

 seniate of lead ; and it is a remarkable circumstance, that this new 

 substance has been discovered by three different persons Professor 

 Del Rio, Professor Sefstrom, and Mr. Johnston in three different 

 countries, Mexico, Sweden, and Scotland, nearly at the same time, 

 and without any knowledge, on the part of one, of what the others 

 had done. 



Mr. Johnston discovered it during the last winter in two minerals, 

 very different in character, but both compounds of lead, probably 

 Vanadiates. The first resembles an arseniate, occurs in small 

 mamillae upon the surface of calamine, sometimes passing into a 

 crystalline form. The second mineral can hardly be distinguished 

 from earthy porous peroxide of manganese. It occurs amorphous 

 and in small rounded forms, often powdering the calamine with a 

 thin black coating, and at times scattered in cavities J. 



15. YELLOW DYE FROM SULPHURET OF CADMIUM. 



M. Lassaigne proposes to use this substance as a yellow dye on silk. 

 If the silk be immersed in a solution of chloride of cadmium for fif- 



* Annales de Chimie, xlv. 70. f Phil. Transactions. 



; Brewster's Journal, v. 167. 



