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THE EIGHTEENTH CENTLRi' 345

However, this denture |-)r()\int>; uiiser\ iceahle, Duchfiteau was ohlit^ed
to put it aside and begin new exjHrmients. I'hese were made with a
special kind ot porcehiin paste used in France tor the first tune m 1740,
which vitrified in baking at 12° to 25° by Wedgwood's p\ronieter, whilst
the usual porcelain required a temperature of 72° to 75° bv the same
test; but the results thus obtained w'ere no better than the preceding
ones, and upon these new failures Duchateau applied to the dentist
Dubois de Chemant, of Paris, for his collaboration. Together they
made fresh attempts, modifying the composition ot the paste h\ adding
a certain quantit\' of pipe clay and other coloring earths to it. 1 hese
modifications enabled them to carry out the baking ot the pieces at a
much lower temperature, and after various experiments the final result
was a denture that fitted the gums well enough, and which, in point of
fact, Duchateau was able to wear.
Encouraged by this success, he tried to manutacture like dentures tor
personages of high rank, hoping to gain money thereb\-, but his want of
knowledge of the dental art prevented him from succeeding in his under-
taking. However, in 1776 he laid this new process before the Ro\al
Academy of Surgeons in Paris, receiving the thanks of that body as well
as an honorable mention.
Whilst Duchateau, discouraged by failure, was giving up all idea of
deriving profit from the practical application of his invention, Dubois de
Chemant, on the contrary, did not cease working tor a moment, in order
to bring the new method of prosthesis to perfection. Little by little he
introduced important modifications into the composition ot the mineral
paste used in the manufacture of the dentures, incorporating therewith
Fontainebleau sand, alicant soda, marl, red oxide ot iron, and cobalt.
His experiments and researches aimed at three principal ends, viz.:
1. The obtaining of mineral teeth otfering all the gradations of color
presented by natural ones.
2. The arriving at a rigorous calculation of the contraction of the mineral
paste in the baking, so as to be able to make prosthetic pieces ot the
desired form and dimensions.
3. The perfecting of the means of attachment of the prosthetic pieces,
and, in particular, of the springs.
By working w^ith intelligence and perseverance, Dubois de Chemant
gradually obtained satisfactory results, and when, in 1788, he published
his first pamphlet on mineral teeth, he had already made dentures and
partial prosthetic pieces for a certain number of persons, who wore them
to great advantage.
As to the chemist Duchateau, from 1776 to 1788, that is, during the
twelve years subsequent to his communication to the Academy ot Sur-
geons, he did absolutely nothing at all. He is, therefore, entitled to the