Mineralogy and Geology. 117 
Chalcotrichite-—This beautiful mineral was found by Mr. C. M. 
Wheatley, filling small cavities in the sulphuret of copper from the 
— copper mine. It was formerly obtained from the Perkiomen 
ead mine. 
Sulphuret of Nickel.—Sulphuret of nickel occurs in Lancaster Co., 
Pa., associated with massive chrome iron, emerald nickel, and a massive 
“violet tale,” in which it is imbedded in small grains and nodules. 
Lievrite-—Lievrite has been found in Monroe, ge Co. : 
at the O'Neil iron mine, in long blade-like crystals, upon crystals of 
magnetite. 
2. On the Angles of Eumanite; by J. E. Tescuemacuer, (from 
a letter to one of the editors, dated Boston, Nov. 11th.) —By careful 
management I have obtained the following measurements of my crys- 
als of eumanite, by usual reflection with my goniometer.* 
é€ on é’, 108° 
é’* ef, 140° 15'¢ OP the smaller crystal. 
‘ 28° 15/ t on the Jarger crystal, 
dete a, eat 
oe On the Silurian System of Central Bohemia; by M. BarRanne 
( ull. Soc. Geol. de France, viii, [2], 150, Jan., 1851.)—M. Barrande 
in his observations on the Silurian System of Central Bohemia, recog- 
8 C, , and E, F,G, H. The lower Silurian consists almost 
Wholly of siliceous and argillaceous rocks, to the nearly total exclusion 
roar with graptolite schists, in which twenty species of graptolites 
ve been detected. Trilobites analogous to those of the Caradoc sand-- 
hae and Llandeilo flags, (corresponding to subdivision D) abound in 
3 iat groups A and B are without fossils, or azoic, and have together 
ee ickness of 24 to 26,000 feet. A is composed of semi-crystallized 
Pye over 1300 feet thick. Its fossils are_mostly trilobites, and they 
hints several subdivisions from C upward are each distinct in their 
; ‘ine bay mostly distinct. The extinction of the fossil species vs : 
