OF THE ELEMENTARY BODIES. 243 
tense heat than carbon to effect this transformation. It may 
now be subjected to a white heat before the flame of a blowpipe 
without inflaming; it may be fused with nitre, even at an inci- 
pient red heat, without producing decomposition; fluoric acid 
has no action upon it; and it cannot be made to enter into 
combination with sulphur. 
Silicium likewise yields a number of isomeric compounds, but 
it is far more evident than in the case of carbon what share its 
allotropic state has in their different nature. We have remarked 
that Siz, combined with sulphur, yields a form of silicic acid 
which is soluble in hydrochloric acid and even in water. Con- 
sequently it is tolerably clear that the isomeric modification of 
silicic acid soluble in hydrochloric acid has Siz for its radical. 
On the other hand, although it cannot be proved by direct expe- 
riment, it is pretty evident that quartz, rock crystal, and the 
artificially prepared insoluble silicic acid, contain the radical Sig, 
the original properties of which are evident in its compounds. 
The mineral kingdom furnishes a number of silicates which 
re entirely soluble in hydrochloric acid. When these are dis- 
solved, one of two things happens; either the acid extracts the 
bases, leaving the silica, or the bases remain insoluble in the 
acid. It has been attempted to attribute the solubility of these 
silicates to the water which they ordinarily contain chemically 
combined ; but the water has nothing to do with it, as is evident 
from the fact that garnet and idiocrase, as they occur in the mi- 
neral kingdom, are perfectly insoluble in hydrochloric acid, and 
only become so when they have been fused into a glass, whereby 
their specific gravity is perceptibly diminished. _ It is thus evi- 
dent that the water they contain proves nothing further than 
that the compound was never exposed to those influences which 
induce the production of the insoluble modification, when at the 
same time the water would have been expelled. In addition to 
these the mineral kingdom yields silicates upon which neither 
acids, nor fusion with bisulphate of potash at a red heat, exert 
any decomposing influence. Glass, which is artificially pro- 
duced, is another example. That the radical of the silicic acid 
in them is Sig is highly probable; but it is not easy to imagine 
why such bases as potash, soda, lime, &c. should assume the 
same indifferent state towards the acid. We shall subsequently 
return to this point. 
The experiments of Frankenheim, which I have already al- 
