fortunately,
however, in approaching the house after leaving the aeroplane, Ned and
Tom had not thought to exercise caution, and, not suspecting anything
wrong, they had stepped on a number of footprints left by the
kidnappers.

But for all that, they saw enough to convince them that several men had
been at the lonely house, for there were many marks of shoes. It was
out of the question, however, to tell which were those of Mr. Petrofsky
and which those of his captors.

"They might have carried him out to a carriage they had in waiting,"
suggested Ned. "Let's go out to the front gate and look in the road.
They hardly would bring the carriage up to the door."

"Good idea," commented Tom, and they hurried to the main thoroughfare
that passed the Russian's house.

"Here they are!" cried Ned, Who was in the lead. "There's been a
carriage here as sure as you're a foot high and it's a rubber-tired one
too."

"GOOD!" cried Tom admiringly. "You're coming right along in your
detective training. How do you make that out?"

"See here, where a piece of rubber has been broken or cut out of the
tire. It makes a peculiar mark in the dirt every time the wheel goes
around."

"That's right, and it will be a good thing to trace the carriage by.
Come on, we'll keep right after it."

"Hold on a bit," suggested Ned, who, though not so quick as Tom Swift,
frequently produced good results by his very slowness. "Are you going
off and leave the airship here for some one to walk off with?"

"Guess they wouldn't take it far," replied the young inventor, "but I'd
better make it safe. I'll disconnect it so they can't start it, though
if Andy Foger happens to come along he might slash the planes just out
of spite. But I guess he won't show up."

Tom took a connecting pin out of the electrical apparatus, making it
impossible to start the aeroplane, and then, wheeling it out of sight
behind a small barn, he and Ned went back to the carriage marks in the
road.

"Hurry!" urged Tom, as he started off in the direction of the village
of Hurdtown, near where the cottage stood. "We will ask people living
along the highway if they've seen a carriage pass."

"But what makes you think they went off that way?" asked Ned. "I should
think they'd head away from the village, so as not to be seen."

"No, I don't agree with you. But wait, we'll look at the marks. Maybe
that will help us."

Peering carefully at the marks of horses' hoofs and the wheel