MINERALOGY. 
withftanding the feveral reafons given, ^vMch 
might induce theni tp examine nearer intp the 
fubjed. 
It was the mine-mafter Mr. Brandt who firft 
difcovered this femi-metal, and defcribed it in the 
abovementioned Hiftory of Semi-metals, in the 
A5ia Upfalienjia for the year 1735. 
The brittlenefs of the cobalt regulus is no proof 
againft its being a femi-metal, that property being 
the bafis on which the diftindion 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, diftind from other earths 
and metallic calces. The experiment of makipg 
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 fhould 
be afcribed to an irreducible metallic earth, 
there is no occafion for this experiment, becaufe 
a cobalt regulus may be prepared fo as to be free 
both from arfenic and iron, the prefence of this 
iaft metal being eafily difcovered by the loadftone. 
It is therefore now unneceflary and ridiculous to 
continue the old definitions of the cobalt, in 
which the Speife, which partly is a cobalt regulus, 
and partly a compound, confifting of nickel, co- 
balt, and bifmuth, united with fulphur and arfenic, 
is either confounded with the femi-metal itfelf, or 
quoted as a proof, that a cobalt regulus cannot 
exifl: in any other manner than as a dead earth in- 
volved in heterogeneous fubftances •, v/hich is the 
fame as to conclude, that no pure copper can be 
produced from the copper regules or fufions, called 
f'iottfien or Spurjten» 
Thcfe 
