was given in an impatient tone--the door
opened and Manoel presented himself.

The young doctor had left his friends on board the jangada at work on
the indecipherable document, and had come to see Judge Jarriquez. He was
anxious to know if he had been fortunate in his researches. He had come
to ask if he had at length discovered the system on which the cryptogram
had been written.

The magistrate was not sorry to see Manoel come in. He was in that state
of excitement that solitude was exasperating to him. He wanted some one
to speak to, some one as anxious to penetrate the mystery as he was.
Manoel was just the man.

"Sir," said Manoel as he entered, "one question! Have you succeeded
better than we have?"

"Sit down first," exclaimed Judge Jarriquez, who got up and began to
pace the room. "Sit down. If we are both of us standing, you will walk
one way and I shall walk the other, and the room will be too narrow to
hold us."

Manoel sat down and repeated his question.

"No! I have not had any success!" replied the magistrate; "I do not
think I am any better off. I have got nothing to tell you; but I have
found out a certainty."

"What is that, sir?"

"That the document is not based on conventional signs, but on what is
known in cryptology as a cipher, that is to say, on a number."

"Well, sir," answered Manoel, "cannot a document of that kind always be
read?"

"Yes," said Jarriquez, "if a letter is invariably represented by the
same letter; if an _a,_ for example, is always a _p,_ and a _p_ is
always an _x;_ if not, it cannot."

"And in this document?"

"In this document the value of the letter changes with the arbitrarily
selected cipher which necessitates it. So a _b_ will in one place be
represented by a _k_ will later on become a _z,_ later on an _u_ or an
_n_ or an _f,_ or any other letter."

"And then?"

"And then, I am sorry to say, the cryptogram is indecipherable."

"Indecipherable!" exclaimed Manoel. "No, sir; we shall end by finding
the key of the document on which the man's life depends."

Manoel had risen, a prey to the excitement he could not control; the
reply he had received was too hopeless, and he refused to accept it for
good.

At a gesture from the judge, however, he sat down again, and in a calmer
voice asked:

"And in the first place, sir, what makes you think that the basis of
this document is a number, or, as you call it, a cipher?"

"Listen to me, young man," replied th