Mineralogy and Geology. 265 
The angles obtained with the common goniometer are as follows :— 
hes plane) : t? 102° 30’-106° 
ist" 
n 
b : i = 138° 20' 
ae = 148° 
1? : 1? (over the summit) —80° 30’ 
m : a? =i 16° 
b :a2 = 134° Bt, 
eee al = 144° Mee: 
b3 : a? = 142° Ps: 
b :a2 =185° Hels oN ee 
The angle mil t? is generally about 102° 30’, although one “erystal 
gave us 106°. a 
The se m in all the specimens, is finely covered with lines, as 
mentioned by 
e new ‘siren of he dor nares at the same locality gave 
us the following angle [See ) 
oa. b2 (ov er b)—86° . 
This form is net usually found ante but a few specimens have been 
obtained with only a slight imperfection. The plane P is frequently 
anes | 
in others it deeply truncates the syoer Many of the crystals ayes — 
joined to the spodumene, in conn n with which it usually occu . 
The mineral is very brittle, and Geccs arises the difficulty of a 
good forms. 4 
2. Age of the Nummulitic formation of the Alpes (from ake 
dress of Sir C. Lyett before the Geol. Soc., Q 
ra eae ean ie 
ther w ght * , aA 
No. 22, 1850. )—In the chronological classification 
posing the crust of the earth, it has been often aske 
to ascribe to the older tertiary epoch, or to the cretaceous system, the. 
great gvmabdlg formation of the Alps, and other parts of f Eufope. ~~ eee 
This much- soniee question,—one, as I shall presently point, tbat, - 
of the’ highest theoretical int in reference to the hypothesis of * the, 
unabated intensity of th : agents of change,—was declared | 
M. Boue, gre: 
tion that the nieatnil ili. rocks: belonged. to. the 
Period, and remarked, ina paper soee 
