. puee 
Fe 
200 achiwerun Ie in. 
is capable of this action, being able to withdraw from silicates a 
portion of their more easily soluble bases, especially potash, and 
to replace them, at least in part, by magnesia and water. Aso- 
lution of carbonate of magnesia in water impregnated with car- 
bonic acid is, as we are aware, distinguished from similar solutions 
of the ee earths by its alkaline reaction, and hence it cannot 
but exercise a far more energétic action upon silicate-masses than, 
for sinned a solution of carbonate of lime in water impregna- 
se with carbonic acid, the action’ of which is acid. In this re- 
t the solutions of the alkaline carbonates will naturally dis- 
hie the most powérful action, put as one phen sr see, they nev- 
er bring about any deposition of substahées.* Hi hly interesting 
proofs may be seen BSG asc a the neighborhood of Bie 
that such a formation of pseudomorphs as is Heré touched upon, 
or one at least resembling it, does in point.of fact occur, and upon 
that I purpose entering upon a future occasion. 
3. Remarks upon certain Petrographic and Geognostic relations. 
When we direct our attention to the formule proposed for the 
micas d the ‘micaceous miner. als; it cannot escape our notice 
that. in very many of them the eee enone eecur as in the 
formule for feldspar, as for instance RSi, R Si, RS 
, thus indicating a certain connect 
ant , 
a s there * 
istic ; distinguished fom 1e micas and the mica- 
ceous mile s, : na Re: as the first have never taken up water 
into their compositi eir1: 1 Poitic ba- 
nt rely of alkalies which do not admit of 
rhereas it would find easier access to the 
micas, which ¢ bontail. magn >a an . peolenye of iron, The 
formula of the, mica from onroe, and Karasulik, and 
probably from rharly other rine es, is, as before mentioned, that 
of garnet ;—the formula of" Abborforss and Sala micas ap- 
proaches the garnet formula, inasmuch as the members thereof are 
* Besides, the ‘of catbo nate of lime in water nts et with capo 
to som compounds otherwisé constituted may, 80 to §] 
the introduction of magnesia, a body, in acertain point of vie 
therewith. 
