Hunt.] 178 [May 4, 
in hardness, condensation, fusibility and chemical characters, which can 
now only be briefly noticed. Of the hard and less fusible metals, chro- 
mium, manganese, iron, nickel and cobalt with p = 26—29.5, give values 
for o == 3.4 — 3.6; while the denser group of palladium, rhodium and 
ruthenium, with p = 52 — 58, and also the still heavier group of plati- 
num, iridium and osmium, in which p = 97 — 99, agree in having v = 
4.5 —4.6. The softer and more fusible metals, gold and silver, give » = 
10 — 10.5. ; the value of » for solid mercury being 13.9, for lead 9.2, for 
tin 8.0, and for cadmium, copper and magnesium 6.5 — 6.9. With these 
it is instructive to compare the values of o for the alkali metals, cesium = 
70, rubidium = 56, potassium = 44, sodium = 24, and lithium = 12; as 
also barium, strontium and calcium, in which » is from 12.5 to 17.5. 
(2.) The tribe of the Galenoidex is conveniently divided into the three 
subtribes of sulphids, selenids and tellurids, which we designate Thiogal- 
enoidex, Selenogalenoides and Tellurogalenoidee. Of these, the first in- 
cludes the typical genus Thionites, embracing the native sulphids of lead, 
silver and copper, together with metacinnabar, stibnite and bismutite ; 
having H=2—3;0=%7—8. The subtribe of the Selenogalenoids in- 
cludes a genus which may be called Eucairites, embracing besides eucair- 
ite (cuproso-argentic selenid) various other selenids of lead, silver, cop- 
per, mercury and bismuth ; H = 2—3; »—8—9.5. The subtribe of 
Tellurogalenoids includes various tellurids of silver, gold, lead, mercury, 
nickel and bismuth, with H = 2.5 — 3.5 ; o = 8 —10.5 ; which we include 
in the genus Tellurites. The soft flexible foliated sulphids like sternbergite, 
argyropyrite, friesite, covelline, and perhaps molybdenite, may constitute 
a second genus of the first subtribe, with the name of Thiophyllites ; while 
tetradymite and nagyagite perhaps may form a similar division of the 
Tellurgalenoids, as Tellurophyllites. 
(3.) In the third tribe we include many sulphids which are near in hard- 
ness, in condensation, and in other characters, to the last, and are chiefly 
sulphids of lead, copper and silver united with sulphid of antimony, of 
bismuth, or more rarely of arsenic. The antimonial species of this tribe 
are represented by the well-known species, bournonite ; from which the 
name of the tribe, Bournonoidex, and the genus Bournonites ; having 
H = 2—3.5; 0» =7— 8.5. The large group of bismuthic species, having 
similar values for H and 2, and many other points of resemblance, of 
which emplectite is a representative, constitute the genus Emplectites. 
These two genera present instructive examples of progressive series, 
especially in the double sulphids of antimony and lead, Sb,8,. »PbS in 
which m has values of 1, 2, 3, 4, 5, 6, and, in a related species, even equals 
12. The species enargite is an arsenical bournonoid, and to this tribe may 
perhaps belong some of the forms of fahlerz or gray copper ore. 
(4.) The next three tribes are distinguished from the two preceding— 
which correspond to, the Glances of the natural-history system—by their 
much greater hardness and condensation, and were included in the order 
seg 
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