urned her back to the mirror.

"It is undoubtedly not a toilette mirror; it is a glass which we use
in chemical experiments to test the highest degrees of heat."

Here the abbe, who wished to air his scientific knowledge, put in--

"As, for example, for burning a diamond."

"Just so," returned Ivan. "That is one of the uses of a concave
mirror; it is necessary for burning a diamond, which requires the
flame of a gas retort."

The countess was grateful for the abbe's remark, for it gave her a
happy inspiration.

"Do you mean to tell me," she said, addressing Ivan, "that a diamond
is combustible?"

"Undoubtedly, for the diamond is, in fact, nothing but coal in the
form of a crystal. With the necessary degrees of heat you can extract
from the patrician diamond ninety florins carat weight, the same
amount of invisible gas or oxide of coal as from the plebeian lump of
coal."

"That is proved by the focus of the magnifier," remarked the abbe.

"I don't believe it," said the countess, throwing back her head.

"I am sorry," returned Ivan, "that I cannot give you a proof that the
diamond is combustible. We do not use such costly things for mere
experiment, but have splints for the purpose, which are cheap in
comparison. I have, however, none of these by me."

"I should like to be convinced, for I do not believe it," repeated the
countess. "Will you make the experiment with this?" As she spoke she
unfastened a brooch from her dress, and handed it to her host. The
centre stone was a fine two-carat brilliant. Theudelinde expected that
Ivan would return it to her, saying, "Oh, it would be a pity to use
this beautiful stone;" and then she would reply, "Then pray keep it as
a slight remembrance;" and in this manner this perverse individual
would have been paid and forgotten. But, to her amazement, the
countess found she had deceived herself.

With the indifference of a philosopher and the courtesy of a gentleman
Ivan took the brooch from its owner.

"I conclude you do not wish to have the ornament melted," he said,
quietly. "I will take the diamond out of its setting, and if it should
not burn you can have it reset."

Without another word he extracted the stone with a little pincers, and
placed it at the bottom of a flat clay saucepan; then he opened the
window, which lay in the full blaze of the sun. He placed the saucepan
upon a stand in the middle of the room and just in front of the
countess; then he took the mag