liens became even
more serious. A new problem faced the Secret Service and its
co-workers. That was to keep the German spies over here from sending
to Germany information that would be of value to her in a military way.
No knowledge of the movements of troops, of fleets, or of supplies must
be allowed to leave America. At all costs the war plans must be kept
secret.

The spies tried to send information to Germany by many different ways,
such as by cable to Denmark, Switzerland, or any other neutral European
nation, and then by telegraph into Germany; or by telegraph to Mexico,
and then by wireless to Germany; or by wireless to a neutral ship on
the ocean, which would relay to Germany by her wireless. The first and
most important thing for the spy in every case was to get his message
out of this country.

To prevent this, the United States established censorships. There were
telegraph censors, watching the wires into Mexico; there were postal
censors, examining the mails; but the most interesting was the cable
censor, who had to keep all the cables free from enemy use. Although
cable censorship was done by the Navy Department, its work very often
overlapped that of the Secret Service. Here is a typical example of
how these two worked together, not correct in details but accurately
showing the method followed in a great many cases:--

In June, 1917, some of General Pershing's first troops sailed from New
York, in number about 15,000 men, in 13 transports. On that very day a
Spanish firm in the city filed a cable to Spain, saying:--

"Quote 13 millers at 15 per cent."

The censor's suspicious mind, always on the alert for something
unusual, saw that this message could easily be a code, which would mean
to the man receiving it, "Sailed, 13 transports with 15,000 troops."

It was too probable to be an accident, thought the censor, and he
decided to watch Mendez & Co. A few days later two more transports
sailed, and Mendez filed three more cables, each containing the number
2, with other figures. The censor promptly put the detectives on the
trail.

The merciless grasp of the Secret Service, which always "gets" its man,
then settled about Mendez. The Spaniard could make no move, day or
night, that was not immediately known to the Service.

In the dead of an autumn night, two agents opened the door of Mendez'
office with a master key, and searched his desk. One man ran over all
the papers, reading them ra