"No, but the trestle is the sticker," some one remarked. "You can't ride on that without being shaken to pieces on the ties."
"I'm not going to try," Joe said. "As I told you, I'm going to take to a rail."
"You'll never do it!" was the prediction. "I thought you were joking when you said that."
"It's no joke for me if I miss getting to the circus on time," said Joe grimly. "And if you watch you'll at least see me start. I'm not going to guarantee where I'll end," he concluded as he took a careful survey of the trestle which stretched out before him for more than a mile.
Joe was not going into this without having thought carefully of it in advance, in spite of the short time it had taken him to make up his mind. He was used to doing that—thinking and deciding quickly. The very nature of his calling made it necessary for him to do this. One does not have much time to make up one's mind when flying through the air from a high trapeze.
Joe felt reasonably sure that if he could get his machine started at a fast rate of speed, and could get it, at that speed, on top of the smooth, and none too wide, rail, he could hold it there. It is a well-known fact in physics that a body in motion tends to follow a straight line, until forced out of that course by some external force. If a stone is thrown it will go in a straight line until the attraction of the earth's gravitation pulls 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.