Page 475 - My FlipBook

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very often the colour of the oxides. It is here necessaiy to
be observed that these two substances are not always equally
good and pure ; but how shall we know it ? There are not
many who analyze these earths by which their principles are
known ; but with us, it is in using them we have known
them. But what must be done to purify them ? This is
what chemistry does not teach us, but what it is indispensa-
ble to know.
The oxides themselves are more or less well prepared,
which clearly explains the variations in their results : to have
such as are good, they must be always taken from a labora-
tory well known to possess merited confidence ; mine, I ob-
tain from that of M. Vauquelin, and I believe they may be
there procured of the proper kind.
In the following paragraphs, we shall occupy ourselves in
enumerating all the objects which are indispensable in the
fabrication of teeth, the properties of each substance in
particular, then the different combinations to each which
we have mutually submitted.
Incorruptible teeth, like human teeth, are composed of two
substances ; one, which is the paste or body of the tooth,
hard and opaque ; the other, vitrifiable, slightly transparent,
in imitation of the living tooth, called enamel.
To commence, the following articles must be procured.
1st.—A very true scale, with which it is possible to weigh
fourths and eighteenths of a grain.
<-2d. A porphyry table, of a foot and a half square, and
more.*

* I for a long time used glass for grinding my substances, but without
; the teeth were more or less cut by it, and their tints were not such
success
as I wished.