MINERALOGY. 235 



withftanding the feveral reafons given, which 

 might induce them to examine nearer into the 

 fubject. 



It was the mine-mafler Mr. Brandt who firft 

 difcovered this femi-metal, and defcribed it in the 

 abovementioned Hiftory of Semi-metals, in the 

 Aft a Upfalienfia for the year 1735. 



The brittlenefs of the cobalt regulus is no proof 

 againft its being a femi-metal, that property being 

 the bans on which the diftinction between the 

 femi-metals and metals is founded. The earth of 

 cobalt is fixed and vitrifiable in the fire, as well as 

 that of copper and iron •, and the colour of its 

 glafs being fo immutable in the fire, proves it to 

 be a particular fubftance, difbindt from other earths 

 and metallic calces. The experiment of making 

 a cobalt glafs from iron or fteel and arfenic, will 

 certainly never fucceed, unlefs the arfenic, em- 

 ployed for that purpofe, has been made from a 

 cobalt ore •, but if the origin of the colour ihould 

 be afcribed to an irreducible metallic earth, 

 there is no occafion for this experiment, becaufe 

 2 cobalt regulus may be prepared fo as to be free 

 both from arfenic and iron, the prefence of this 

 lafi metal being eafily difcovered by the loadftone. 

 It is therefore now unnecefTary and iidiculous to 

 continue the old definitions of the cobalt, in 

 which the Speife, which partly is a cobalt regulus, 

 and partly a compound, confjfling of nickel, co- 

 balt, andbifmuth, united with fulphur and arfenic, 

 is either confounded with the femi-metal itfelf, or 

 quoted as a proof, that a cobalt regulus cannot 

 exift in any other manner than as a dead earth in- 

 volved in heterogeneous fubftances ; which is the 

 fame as to conclude, that no pure copper can be 

 produced from the copper regules or fufibfi?, called 

 Tfottjlen or Spnrjten, 



Theft 



