91 
from St Pardoux in Auvergne. 
the method used by Berzelius in the analysis of topaz. A very 
slight precipitate was thrown down by means of muriate of lime 
and caustic ammonia, which was composed of alumina and silica. 
It was treated with sulphuric acid in a platina crucible, upon 
which a plate had been put, which was covered with a stratum 
of wax, and bared in some places ; but there appeared no traces 
of etching, when, after standing some hours upon a warm fur- 
nace, the glass had been taken off and washed. 
It would be useless to give a mineralogical formula for the 
composition of this mineral. For this purpose its purity would 
require to be better ascertained than was in reality possible. 
I have only to observe that the quantity of oxygen in silica is 
nearly double that in the other bases together. 
The preceding analysis, I think, proves such an affinity be- 
tween the pinite and mica, in regard to chemical composition, 
that they can no longer be considered as generically separate. 
The circumstance that pinite contains no fluoric acid, cannot be 
considered as an essential difference, when it is observed that 
even those varieties of mica which occur in primitive limestones, 
contain very little of that acid, or are entirely destitute of it. 
according to the experiments of II. Hose : fluoric acid ought 
not therefore to be considered as an essential constituent of mica. 
It is possible that the pinite, during the unknown alterations 
which it has evidently undergone, may have lost its original 
fluoric acid, or that this substance may have combined with an 
animal matter. 
Aut. VII '.—On the Geognostical Phenomena at the Temple Of 
Serapis. 
[[The singular phenomena exhibited at the Temple of Serapis have 
for a long period engaged the attention of geologists. In the 
Illustrations of the Huttonian Theory (§ 3[)7, 398) the following 
observations occur, from which it appears that Breislac consi- 
ders them as connected with changes in the level of the ocean, 
while Professor Playfair views them as illustrating risings and 
sinkings of the land. 
