92 J. D. Dana on a connection between 
2. Hexagonal species, and _ number 3.—Hexagonal species 
have been stated to occur among the sesquioxyds (as Fe?03, 
Al?03, Cr?03); the dinthictea — in beryl, eudialyte, dioptase 
pyrosmalite, chabazite, gmelinite) ; and the carbonates (in cal- 
cite, and the allied species) ; in ik compounds the number of 
atoms of oxygen is 3, or a multiple of 3. Other examples are: 
e and proustite, 3AgS+-(Sb, As)*S3, in which the number of atoms of : ) 
Pyrargyrit 
sulphur is 6; gibbsite AIH?; alunite KS+38AiS+6aq; apatite 30a°P+4CaCl; 
coquimbite #824909; Al?013+12aq ; MgS+-6aq ; AIS?+-27aq ; SrOS205-+-4aq, 
and the corresponding salt of lime, and of lead; KN; NaN; (Ca+H2)€; Ag0, 
C107+-4H ; ream ea Baier ca Ear inh oa ae 
of t the hexagonal sesquioxyds, Fe?0*, Al?03, Cr?03, Ripe 
the hexagonal protoxyd ZnO, ‘similar in angle. A Bie the 
bs of ones aoe and writin g the formula Zn*O%, it then 
he sesquioxyds, 8 of O. This view of the protoxyd | 
staan signifies sqee dog m of R Agai 
graphite, or hexagonal Nagy has en shown ms oe its atomic 
erieat penely three ti at of ordinary carbon; 
NisSbe (br isha ee 
system.—The number of a negative — 
sisal’ in isometric species a pears to oe ithe 1 rs 3,4,0r8 
multiple of 3 or 4; and this iversity accords with the ‘twofold 
also deutox aonede ps Rae sates ; in laweites dtp also in— / 
MgB, or boracite; Xs; Sb; Nai; KBr; Nafie; MiG1-+ coq; Oudl+6os 
CoBr+6aq; AmCl+SnCl?; KCy+AgCy; 3Na+Gr62+-9aq; the alums, 
have 160, besides 240 in the water; em NaW+Www. 
_ Important chemical and crystallographic conclusions flow from | 
