Hunt.] 176 [May 4, 
small additions would, however, if found in ordinary analyses of mineral 
species, be disregarded, as impurities not essential to the composition. In 
like manner the small amounts of fluorine, of chlorine, of hydrogen, of 
boron, and of phosphorus, so often met with in native silicates, are not to 
be looked on as accidental ingredients, but as essential parts of highly 
complex integers. Farther and more critical chemical analyses are neces- 
sary before we can fully know the constitution of dense insoluble species, 
and the great difficulty is to decide how far these small portions of ele- 
ments are due to impurities, and how far they are elements necessary to 
the constitution of the species; questions which in many cases can only 
be solved by much care and study. 
6. The non-oxydized metalline minerals, embracing the metals, their 
alloys, and all their compounds with sulphur, selenium, tellurium, phos- 
phorus, arsenic, antimony and bismuth, are, in the natural-historical classi- 
fication of Mohsand his followers, comprised in four orders—-Pyrites, Metals, 
Glances and Blendes (Pyrites, Metalli, Lamprites and Minia of Breithaupt). 
All of these we have included in Class I, METALLACE A, embracing 
but a single order MrratuatTa, which is, however, divided into two 
suborders. The reasons for including the metals and their various alloys 
in the same order with sulphids, selenids, tellurids, phosphids, arsenids, 
antimonids, bismuthids, sulpharsenids, sulphantimonids, etc., are two-fold ; 
first, the resemblances between the typical and malleable metals, such as 
gold, silver, lead, copper, nickel, and iron, and the elementary metalline 
species, tellurium, arsenic, antimony, and bismuth, are such that the com- 
pounds of these with the metals above named cannot well be separated 
from alloys. Another reason is to be found in the complex nature of many 
artificial products known to us as metals. Thus the cast irons from the 
blast-furnace are compounds, apparently homogeneous, of iron with small 
quantities of sulphur or of phosphorus, with silicon, and with carbon ; 
while copper may in like manner contain small quantities of phosphorus, 
of arsenic, or of silicon. These constitute sulphids, phosphids, arsenids, 
silicids and carbids of iron and of copper, in which the amounts of the 
added elements, though proportionally small, nevertheless, modify pro- 
foundly the character of the compounds, affording additional illustrations 
of the principle insisted upon above in speaking of oxydized species. 
". The division of the Metallata into two suborders, which we have des- 
ignated Meta]lometallinea and Spatometallinea, is based upon the radical 
differences which distinguish the great groups of the Glances and the 
Blendes. The first suborder, like the Glances, includes alike simple sul- 
phids like galena, argentite, chalcocite, metacinnabar, stibnite and molyb- 
denite ; selenids like eucairite and clausthalite ; tellurids like altaite, syl- 
vanite and tetradymite ; sulpharsenids like enargite ; sulphantimonids like 
pbournonite and stephanites; ulphobismuthids like emplectite and kobel- 
lite. To the Metallometallinez also belongs the order Pyrites of Mohs. This 
not only includes the harder simple sulphids as marcasite, pyrite, siegen- 
