Scheerer on Isomorphism. 201 
similar though otherwise combined. This would go to explain 
the circumstance of garnets occurring imbedded in such numerous 
instances in mica-slate 
In conclusion, I now come to the question put already at the 
commencement of this paper, pets is it then, since aspasiolite and 
cordierite occur close together, t ine is not in like man- 
ner associated with olivine? It wil be readily conceded that wa- 
ter as’ well as all the other bases in question, cannot but have been 
present at the formation of aspasiolite and serpentine, (and indeed 
of all hydrous minerals, occurring as admixtures in primitive for- 
mations. But why was it now that that was taken up by the 
serpentine mass so through and through that not even the small- 
only partially, and became thereby converted to aspasiolite? 
Before replying to this question we must revert to the formula pro- 
posed for these minerals, 
Olivine, > RSiv om a ' RAM 3R Si. 
Serpentine, (R): aN 
In olivine, 3 atom: of | 
this ground it must i for water tomake it way it 
vine than into cordierite. But vars water, at the formation m of 
serpentine actually prevented a portion of’ the magne nesia from com 
bining in its place with silica, is proved beyond a doubt by foe 
namely, that in the Snarum serpentine a mineral occurs imbedded 
in great’ abundance ( hydrotalcite), the constituents of which are 
hydrate of magnesia and carbonate of “magnesia. 
therefore have been no absence of magnesia at the formation of 
serpentine,and the water, so to speak, have been thus compelled to 
be taken up by the silica, but the water, in consequence of its basic 
properties, has in truth SUPPLANTED a ‘portion of the magnesia, 
a 
OF THE QUESTION. The water could not exert a similar influence _ 
upon rae  copdierite mass from hot penetrating it so readily, but 
was S prin taken up thereby where magnesia was wane 
= 
bo ae 
