6 14 Mr. woulfe’s Experiments to aj certain 
this mineral is compofed of filver, fulphur, and arfenic ; 
fome, of filver fulphur, arfenic, and fixed alkaly; 
others, of filver, arfenic and acid of fea-falt; but Melfi 
cronstead and le sage aflert, that it is Compofed of 
filver and acid of fait only. 1 know of no experiments 
that have been made public with a view to determine 
this affair, except thofe of M. le sage; but he and I 
differ widely in the refult of our experiments. 
EXPERIMENT VII. 
Two drams of brown, native horn filver, cut into very 
thin flices, and well ground with the like quantity of 
fixed alkaly of tartar and a little w r ater, treated as in the 
firft experiment, produced forty-three grains of neutral 
fait, compofed of flat cubic cryftals of regenerated fea- 
falt, intermixed with brown cryftals of tartar of vitriol ; 
this laft did not appear to be above one-tliird of the firft. 
The brown colour of the horn filver is owing to an 
ochre of iron ; a thin flice of it, viewed through a mag- 
nifying glafs, looks in fome parts of a lmooth pearly 
colour, but in others of a powdry brown one. 
The filver, which remained after this operation, had 
the fame texture and filvery appearance as that of the 
firft experiment. It wxis digefted with diftilled vinegar, 
then filtered and evaporated to one- fourth, with a deiign 
to diflipate the excefs of acids. A frelli infufion of galls 
mixed with it becomes of a dark purple colour, which 
precipitates; an inconteftible proof of the iron it contains, 
i Silver. 
