hundred pounds," he suddenly whispered eagerly.
With that my suspicions returned. The thing might, after all, be
merely a lump of that almost equally hard substance, corundum, with
an accidental resemblance in shape to the diamond. Or if it was a
diamond, how came he by it, and why should he offer it at a hundred
pounds?

We looked into one another's eyes. He seemed eager, but
honestly eager. At that moment I believed it was a diamond he was
trying to sell. Yet I am a poor man, a hundred pounds would leave
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,
and worthless as jewels. Now I, you know, have given up my life to
this problem--given my life to it.

"I began to work at the conditions of diamond making when I
was seventeen, and now I am thirty-two. It seemed to me that it
might take all the thought and energies of a man for ten years, or
twenty years, but, even if it did, the game was still worth the
candle. Suppose one to have at last just hit the right trick
before the secret got out and diamonds became as common as coal,
on