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DIAMOND.                                     101
Carbon is combustible and evaporates, when subjected to strong heat, but it never melts.
Carbon mixes with certain liquids, but never dis­solves.
Carbon and the diamond crackle in the fire, but never soften.
How then, in the present state of our knowledge, can the transformation of carbon into diamond be eifected ?
It is self-evident, that to this end is necessary either the discovery of a new liquid or the concentration of such heat as no chemico-physical instrument has yet produced.
It appears that in the formation of the diamond Nature uses heat of an extremely high temperature, but her power infinitely exceeds that of man.
In 1828 Cagnard de la Tour sent to the Academy of Sciences at Paris ten tubes full of small crystals, of a brown colour, which he presented as crystallized car­bon ; after many experiments they proved to be merely various transparent silicates, harder than quartz, less so than diamond, and also incombustible.
A short time after, Gannal tried various experiments with phosphorus and sulphur; but the trial which appeared most likely to conduce to the desired end was that of the celebrated Desprez, who hoped to suc­ceed in melting carbon by uniting all the voltaic piles in Paris, in order to concentrate the heat to a degree never previously attained, over pieces of carbon en­closed in a glass receiver. Under this terrible tempe­rature the carbon evaporated entirely, excepting that