PHOSPHORESCENCE OF DIAMOND
Ordinary oxidising reagents have little or no effect in restoring the colour.
The superficial dark coating on a diamond after exposure to molecular bombardment I have proved to be graphite. M. Moissan has shown that this graphite, on account of its great resistance to oxidising reagents, cannot have been formed at a lower temperature than 36000 C.
It is thus manifest that the bombarding electrons, striking the diamond with enormous velocity, raise the superficial layer to the temperature of the electric arc and turn it into graphite, whilst the mass of diamond and its conductivity to heat are sufficient to keep down the general temperature to such a point that the tube appears scarcely more than warm to the touch.
A similar action occurs with silver, the superficial layers of which can be raised to a red heat without the whole mass becoming more than warm.
