Properties of some Minerals and their varieties, 259 
with copper. Taking into consideration the position of the 
copper employed by us, as just explained, these minerals must 
stand nearer the positive end of the series (except so far as 
oan! non-conducting power was the occasion of the negative 
result). 
Argentite Ag,S isometric. 
Acanthite Ag,S orthorhombic. 
Sphalerite ZnS isomet, hemihedral. 
Alabandite Mns isometric, 
Hauerite MnS, zs 
Rutile TiO, orthorhombice. 
Brookite LiGy monoclinic, 
Antimonite 
Boulangerite Pb,Sb,8 
ite Pb, Bi, Sb. 8, 
Sartorite Ss 
2™4 
This list of minerals investigated embraces unfortunately the 
majority of those substances from which we expected to throw 
great light upon our subject. : 
In the dimorphous group of the silver sulphids the change 
of form does not correspond to any variation in the thermo- 
electrical properties. Argentite and acanthite are in this re- 
spect similar, so also rutile and brookite. In sphalerite, also, 
the form seemed to have no influence, although right and left 
hemihedrism is distinguishable. Alabandite and hauerite were 
selected in order to show the influence of an increasing per- 
centage in sulphur. The group boulangerite, kobellite, sartor- 
ite and antimonite were investigated in order to ascertain their 
relation to galenite ; but no essential differences were observed. 
It is to be mentioned that (in consequence of their containing 
antimony) they stand nearer the positive end of the series, 
while galenite, on the other hand, is strongly negative. 
B. The following minerals* are positive (+), or negative (—), in 
contact with copper : 
1. Bismuth compounds. [Bi—] 
Bismuthinite i,S — Sweden. : 
Tetradymite Bi,(TeS), | — Schubkau, Orawitza. 
*It is ed, in examining this table, that arsenic, antimony, and tel- 
lurium, os ue pers + in cx, Homie stotee while in composition they 
are generally negative. 
