said. "Do you know anything
about the city?"

The boys admitted their ignorance.

"Then your first job is to get acquainted with New York. Get some maps
and guide-books. While you are getting your bearings you can establish
a wireless watch. I have a number of outfits in different parts of the
city. For the next week or two, while you are getting acquainted with
the city, I want you to maintain a twenty-four-hour watch at a place I
shall send you to. Divide the time among you so that some one is
listening in all the time. Here are the call signals of all the
legitimate plants you will hear, either on land or water. Pay
particular attention to call signals. If you catch one not in this
list, be sure to get every word sent and let me hear from you at once.
We have other operators listening in for messages of the usual
commercial wave lengths and for very long wave lengths, so you need
watch only for messages of less than three hundred meters."

He wrote an address on a slip of paper and gave it to Captain Hardy.
"Go there," he directed. "A wireless outfit has been installed and
accommodations await you."

He took the slip of paper from Captain Hardy and wrote some figures on
it. "That," said he, "is my private telephone number. But do not
bother me unless you get hold of something important."

In another moment the wireless party found itself in the rush and roar
of lower Broadway.

CHAPTER V

THE MESSAGE IN CIPHER

The house to which Chief Flynn had directed the wireless patrol proved to
be a private residence on a side street that ran between Central Park and
the Hudson River. It was a tall house, standing two stories higher than
any other structure in the block. Like most of its neighbors it had
evidently seen better days. In places the brownstone front was cracked
and great chips had flaked off. The broken stones in the long flight of
steps that led up to the first floor were patched with colored cement
that had faded so the patches stood out baldly. The brass handrail above
the stone balustrade was battered and dirty. Altogether it was not a
very attractive looking place.

The old lady who opened the door eyed them sharply.

"A gentleman named Flynn recommended me to your place," said Captain
Hardy. "We shall need accommodations for quite a while."

"You must be the gentleman from Washington that he 'phoned me about. You
are Captain Hardy?"

"I am."

"Come in," said the la