452 Miscellaneous Intelligence. 
word, i in all vitreous or porphyritic rocks, hydrated or not, the silica 
is in combination, forming a compound, not definite, which the alkali 
attacks, and which is the paste of the rocks. 
The waters of infiltration which penetrate rocks contain always 
small proportions of alkaline salts, even near the earth’s surface ; and 
hence it is obvious that these salts should contribute towards the de- 
composition of the rocks and the formation of pseudomorphs. But at 
a small depth below, the waters are more largely etaroat with alkaline 
salis, and both temperature and pressure increase rapidly ; they may 
attack, therefore, quite strongly, the rocks with which they come in 
contact ; as happens notably ‘with mineral waters, geysers, ‘and other 
results of volcanic action. Consequently the action of alkalies or of 
alkaline salts on rocks plays an sh aphe part, not only in the forma- 
tion of pseudomorphs, but also in the chemical reactions which take 
4, On the Prosopite of Scheerer ; by Jamrs D. Dana. — Prosopite 
is described as a new mineral by Scheerer_in Poggendorff’s Annalen, 
No. 10, 1853, p. 315. The —— occurs at the Tin mines of Alten- 
berg in crystals altered mostly to a kaolin; and from some qualitative 
trials of unaltered cepa it is reat: to consist of aluminium, cal- 
cium, fluorine and water. It had been regarded as a pseudomorph after 
Heavy Spar: Sohieeter. recognizes its relations to that species in the 
132°, 1164°. Unlike Heavy Spar, the crystals are hemihedral. The 
faces of the Somes: are dull, and admit of measurement only with the 
common goniomete Scheerer suggests that the formula may be 
CaF-LAIFS, aoslagoes to that of Heavy Spar which is CaO-+-SO$. 
This comparison with Heavy Spar does not exhibit its true affinitie 
In fact the angles are almost identical with those of Datholite, with 
which it also agrees in its hemihedral character. ‘The following angles 
show this resemblance. The planes of Datholite oo referred to will 
be learned from the figures on page 215 of this volum 
_ Datholite. — E _Prosopite. 
42 : 2 = 76° 44’ i2 : i2 = 17°-78° (=d : d! of Scheerer.) 
O : 22 = 135° O : 22= 135° (=C:B 
2 : 2 (adj.) = 131° 52’ 2: 2 (adj.) = 132° (=z: 2’) 
i : 2t (top) = 115° 26 = : 2 (top) = 1164° (=o : 0’) 
23 : 23 (adj.) = 118° 9 23 : 23 (adj.) = 119° =(t: ¢’) 
Owing to the disguised character of the mineral, it was named Pros- 
opite from go0uzevor, a mask—a name ceriainly well deserved. 
The symbols of the planes used above become Naumann’s on insert- 
a P, and putting & fori. The plane i3(aP%¥) is that usually 
considered aP. 
5, Geological Survey of Tennessee.—The State of Tennessee has 
ordered a Geological Survey of its territory, and appointed to the 
work Prof. J. M. Safford of Cumberland University, Tennessee. ‘1 he ap- 
pointment is a most excellent one. Professor Safford is well prepared 
for the duties, and his final Reports will, Ht hee doubt, ae? both re 
uable and honorable to the State and to re 
