it down.

But in Joe's case gravitation would have no effect, as he would be on
the ground all the while, or what was practically the ground. What he
would have to guard against would be a deviation of more than an inch
from left or right. If he swerved ever so little, his machine would
leave the rail and he would either plunge over the side of the high
trestle, or he would find himself bumping over the ties.

"And I wouldn't want either of those things to happen," mused Joe, with
a grim smile on his face.

But Joe Strong knew that a swiftly moving motor-cycle or bicycle has a
very strong tendency to follow a straight course. It is easy to keep
one's bicycle in a straight line when going fast. There is hardly any
need of balancing, and one may ride along even without having the hands
on the steering bars.

A motor-cycle moves much faster than a bicycle, and so has a greater
chance of keeping in a straight line. This was what Joe was counting on
when he proposed to ride on the narrow rail over the high trestle.

He must work rapidly now. It was drawing nearer to the time for the
opening of the afternoon performance, and Joe felt that his absence up
to this time must be worrying the ring-master, who liked his performers
on hand in plenty of time before the show was to open.

Joe looked about for a means of getting up on the rail. It would not do
to have some one hold his machine there, and so start. For that would
mean his front wheel would swerve more or less because of an endeavor
to get his balance, and he would be off the rail almost as soon as he
was on it.

"I've got to get a flying start, and hit the rail at a good pace,"
reasoned Joe. "How can I do it?"

Almost at once the answer came to him. Near the place where he and the
curious villagers had mounted to the railroad embankment were some
planks. They had been taken out of a cattle-guard, to be replaced by
new ones.

"I can make a temporary runway of the old planks," reasoned Joe, "and
guide myself to the rail with them."

He quickly explained to the men and boys his need. They grasped the
idea at once and began to help.

In a few minutes a platform of planks was laid on either side of a rail
where it was spiked to the sleepers which were embedded in the cinders.
The trestle started a few feet beyond where the temporary runway, or
guiding planks, ended.

Joe used three planks--that is the runway was three planks wide, and
they were laid one on ei