Sèvres ware, are almost exclusively formed of this substance.
And what is clay?
To
answer this question categorically is impossible, because there are
comprehended under that name a multitude of mixtures, whose composition
is extremely variable ; but the only fact important for us to know here
is that the principal constituent element of clay is alumina.
In these modern times industry has been enriched by an important conquest, aluminium, that
new metal which, whether used alone or in combination with other
metals, lends itself with complete success to the manifold wants of
the industrial arts. It is a discovery and creation for which our epoch
is indebted to the French chemist M. Henri Sainte-Claire Deville.
If
this metal is combined with the oxygen of the air, the metal
disappears, and is transformed into the rust of aluminium; exactly as
the brilliant and metallic iron is transformed into iron rust under the
same conditions; only that aluminium rust is white instead of red. This
white rust is pure alumina.
Now
this alumina exists in a prodigious quantity, not only in vegetable
mould, but also in a large portion of the rocks of our globe. Generally
it is mixed with iron rust, which gives it a red colour, or
