a visible gap in my fortunes and no sane man would buy a diamond by
gaslight from a ragged tramp on his personal warranty only. Still,
a diamond that size conjured up a vision of many thousands of
pounds. Then, thought I, such a stone could scarcely exist without
being mentioned in every book on gems, and again I called to mind
the stories of contraband and light-fingered Kaffirs at the Cape.
I put the question of purchase on one side.

"How did you get it?" said I.

"I made it."

I had heard something of Moissan, but I knew his artificial
diamonds were very small. I shook my head.

"You seem to know something of this kind of thing. I will
tell you a little about myself. Perhaps then you may think better
of the purchase." He turned round with his back to the river, and
put his hands in his pockets. He sighed. "I know you will not
believe me."

"Diamonds," he began--and as he spoke his voice lost its faint
flavour of the tramp and assumed something of the easy tone of an
educated man--are to be made by throwing carbon out of combination
in a suitable flux and under a suitable pressure; the carbon
crystallises out, not as black-lead or charcoal-powder, but as
small diamonds. So much has been known to chemists for years, but
no one yet had hit upon exactly the right flux in which to melt up
the carbon, or exactly the right pressure for the best results.
Consequently the diamonds made by chemists are small and dark,