high
board fence, surrounding some vacant lots, he heard some one whisper
hoarsely:

"Here he comes!"

The young inventor was on his guard instantly. He jumped back to
avoid a moving shadow, but was too late. Something struck him on the
back of his head, and he felt his senses leaving him. He struggled
against the feeling, and he realized, even in that exciting moment,
that the thick collar of his heavy overcoat, which he had turned up
because of a cold wind, had, perhaps, saved him from a broken skull.

"Hold him!" commanded another voice. "I'll go through him!"

The packages dropped from Tom's nerveless fingers. He felt himself
sinking down, in spite of his fierce determination not to succumb.
He felt several hands moving rapidly about his body, and then he
struck blindly out at the footpads.

CHAPTER XI

OFF FOR THE FROZEN NORTH

Tom Swift felt as if he was struggling in some dream or nightmare.
He felt strong hands holding him and saw evil faces leering at him.

Then gradually his brain cleared. His muscles, that had been
weakened by the cowardly blow, grew strong. He felt his fist land
heavily on some one's face. He heard a smothered gasp of pain.

Then came the sound of footsteps running--Tom heard the "ping" of a
policeman's night-stick on the sidewalk.

"Here come the cops!" he heard one voice exclaim.

"Did you get it?" asked another.

"No, I can't find it. Cut for it now!"

They released the young inventor so suddenly that he staggered about
and almost fell.

The next moment Tom was looking into the face of a big policeman,
who was half supporting him.

"What's the matter?" asked the officer.

"Hold-up, I guess," mumbled the lad. "There they go!" he pointed
toward two dark forms slipping along down the dimly-lighted street.

The officer drew his revolver, and fired two shots in the air, but
the fleeing figures did not stop.

"How did it happen?" asked the policeman. "Did they get anything
from you?"

"No--I guess not," answered Tom. He saw the packages containing his
purchases lying where they had fallen. A touch told him his watch
and pocketbook were safe. The precious map was in a belt about his
waist, and that had not been removed. "No, they didn't get
anything," he assured the officer.

"I came along too quick for 'em, I guess," spoke the bluecoat. "This
is a bad neighborhood. There have been several hold-ups here of
late, but I was on the job too soon for these fellows.