eee We = ee ; i to Be RE 
: 
* Repti Phenomena about Lake Bigpond 83. 
* interest to the subject of atomic volume among minerals, I have’ 
eee calculated the atomic volume of these varieties. 
wi (1.) iy " 2.) 
Siz = 115462 Siz et 1154-62 
Ald$ = 149-26 Az = 427-87 
Fe? 767-45 Fet _ 833-338 
: Feig3+ = 828-68 Fe1$% = 840-00 
— Natt = 61°36 Na}? = 5163: 
3 = 337°50 1134 - 365°62 
3298'87 8173-07 
hese two numbers, which are the atomic weights of the two 
varieties, divided by the specific gravity 2°69, give for (1), the 
atomic volume 1226°35, and for (2), 1L80-, the difference be- 
tween which is about th. If we go farther, and divide these 
numbers by the number of atoms of the elements in each variety, 
we shall obtain the C atomic volume, as this term is used by Mr. 
na. In one case we get 53°32 and in the other 50-21. If ref- 
erence is now made to the tables of atomic volumes given by 
Mr. Dana in the American Journal for March, 1850, p. 242, it 
will be seen that these numbers are nearly identical with those 
given by him for three varieties of talc, a mineral which the one 
now under consideration resembles in many important characters. 
On the contrary, chlorite, a mineral to which this one is so inti- 
mately connected as to have been mistaken for it by an eminent 
mineralogist, gives altogether a different number. ‘T have calcu- 
lated the C atomic volume of chlorite from one of Kobell’s anal- 
yses which gives the forme la 
§i2+-Al+Me4#4 Pet He 
and obtained 43-6. "The hisingerite from Ridderhyttan also re- 
Sembles this mineral very closely. Its formula, according to Hisin- 
ger and Kobell, is Fe Sit+¥e Si+6H; and specific gravity 3-045. 
Its ordinary atomic volume is 1077-05 5, and its C atomic volume 
ae ne approaching that of chloeles: instead of that of this 
min 
bas: of the Coll. of Phys., Crosby st.. New York, April 1, 1850. 
Arr, XIII.— The Bak es Phenomena about Lake Superior ; 
y Prof. Acassiz. 
[We cannot —— notice the very valuable and interesting 
work of Prof. Agassiz and his associates upon the e Superior 
Region,* than by siting one of its chapters. ‘The following ob- 
servations on the Erratic Phenomena of the region constitute 
Chapter X, of the work, pages 395-416. ] 
Pg ith, f£ at, 1 Pe. 4 
The title of t 
ueenere vcd ie 
last number, p. 455, 
