rbairn slowly. "There's some reason, of course, something
perhaps in the make of the glass."

He held one of the tubes up to the light. There was nothing to
distinguish it from any one of the tubes in which small tabloids are
sold by chemists.

Hillyard got out of his bureau the letter in which these tubes were
mentioned.

"'They have been successful in France,'" he said, quoting from the
letter. "The scientists may be able to make something of them in Paris.
This letter and the tubes together may give a clue. I think that I had
better take one of the boxes to Paris."

"Yes," said Fairbairn gloomily. "But----" and he shrugged his shoulders.

"But it's one of the ninety per cent, which go wrong, eh?" Hillyard
finished the sentence with bitterness. Disappointment was heavy upon
both men. Hillyard, too, was tired by the tension of these last
sleepless days. He had not understood how much he had counted upon
success.

"Yes, it's damnably disheartening," he cried. "I thought these tubes
might lead us pretty straight to B45."

"B45!"

The exclamation came from Jose Medina, who was leaning against the
doorpost of the saloon, half in the room, half out on the sunlit deck.
He had placed himself tactfully aloof. The examination of the cases was
none of his business. Now, however, his face lit up.

"B45." He shut the door and took a seat at the table. "I can tell you
about B45."

CHAPTER XVIII

THE USES OF SCIENCE

It was Hillyard's creed that chance will serve a man very capably, if he
is equipped to take advantage of its help; and here was an instance. The
preparation had begun on the morning when Hillyard took the _Dragonfly_
into the harbour of Palma. Chance had offered her assistance some months
later in an hotel at Madrid; as Medina was now to explain.

"The day after you left Mallorca," said Jose Medina, "it was known all
over Palma that you had come to visit me."

"Of course," answered Martin.

"I was in consequence approached almost immediately, by the other side."

"I expected that. It was only natural."

"There is a young lady in Madrid," continued Jose Medina.

"Carolina Muller?"

"No."

"Rosa Hahn, then."

"Yes," said Jose Medina.

Jose rose and unlocking a drawer in his bureau took out from it a sheaf
of photographs. He selected one and handed it with a smile to Hillyard.
It was the portrait of a good-looking girl, tall, dark, and intelligent,
but heavy about the feet, dressed i