Mineralogy and Geology. 445 
The oxyd of manganese corresponds nearly to the sesquioxyd, the, per- 
centage being manganese 70°63, oxygen 29- ’ it 
Another ore from Bimlapatam, afforded, besides impurities, red oxyd 
of manganese 76-117, oxygen 0°655, which is a little less oxygen than 
Is required to make it a sesquioxyd. 
Franklinite of New Jersey.--Mr. A. C. Farrincton, (Proc. Amer. 
Assoc., vi, 241) has observed the interesting fact, that the Franklinite 
of the large vein is strongly magnetic where it adjoins the igneous rock 
enclosing it, (being taken up by a magnet when pulverized) but gradu- 
ally diminishes in its magnetism on receding from the walls of syenite, 
it being perceptible only for four feet. Mr. Farrington inferred that 
the metal near the walls was protoxyd mainly and peroxyd remote 
from them, and a mixture in other parts. 
_Triphyline of Bodenmais.—RammeE.ssexc has analyzed this mineral 
(Pogg. Ann., Ixxxv, 439) with the following result. 
Fe Mn . 2a.) ok: ee 
Analysis I, 89°35 4142 948 708 4107 O85 128 —-== 99°98 
Mean of four anal, 40°72. 39:97 980 728 145 058 —- 0:25==100+05 
22°82 887 219 400 037 010 
Formula for the mean result, 3k? f+2R4 8; for the first analysis 
which gives the oxygen ratio 10:7, R* B+ Rs B. 
The triphyline on alteration, loses its alkali, takes up water and oxy- 
gen, the iron and manganese becoming peroxyds. The mineral fro 
Norwich, Mass., and Damour’s Adluaudite are of this kind. The Trip- 
lite. of Limoges, according to Berzelius, has the formula Ré B. if 
, Tbe Heterosite of Limoges, or a brownish violet mineral from this 
locality, afforded Rammelsberg, ¥ tt J 
Fe 
€ ssi 
: 32°18 31:46 30°01 6°35 
giving the formula #7 £446E But reckoning it as a protoxyd com- 
pound, the formula becomes, excluding the water, R* B+Rs P. 
This of viewing them 
ity is still a fact, for many of the erystals, (we speak from observation) 
ive the angle M : T, 90°, and these crystals include the smaller ones, 
Which are most likely to give the normal form. There is therefore 
better evidence, that the crystals are right than oblique ; and we believe 
from our observations that the right prism is also the more prevalent 
form ere is some doubt as to some of Prof. Shepard’s angles. 
The angle P:M (OP: a@ P’ a) is given at 90°, while M make 
