“You notice the two strings cross at the 2.45 line,” continued Mr. Schofield, “between Musselman and Roxabel. What does that mean?”
“It means the trains will meet there.”
“But they can’t meet out there on a single track. They’ve got to meet at a station where there’s a siding. So we’ve got to hold Number Three at Musselman three minutes until Number Four can get past—in other words, we’ve got to change the red string a little, like this,” and he drove another pin on the 2.42 line at Musselman, and tied the red string to it. “That provides a meeting place for those two trains. Now let’s go ahead with the others.”
White strings representing all the east-bound passenger trains were put on the board in the same way. All of them ran more or less parallel with each other, the faster trains inclining more toward the perpendicular and the slower trains more toward the horizontal. To each string was attached a little tag bearing the number of the train, and that being done, the superintendent declared it was time to adjourn for lunch.
An hour later, the work of stringing the west-bound passenger trains was taken up, the red cord being used to represent them. As they necessarily ran in the opposite direction, these strings crossed the strings representing the east-bound trains, and each of these crossings indicated a meeting-point. When the strings were first put on the board, it was found that many of them, as had been the case with those representing trains Three and Four, crossed between stations, and as it is against the rules of all railroading to permit two trains going in opposite directions to meet on the same track, the running time of the trains had to be so altered that the meetings occurred at a station, or at least at a place where there was a siding, so that one train could pull in out of the way of the other. The through passenger trains, which are given preference, were so timed that they could run from end to end of the division without getting out of the way of anything; the accommodations usually had two or three short waits, but so carefully were these timed that their passengers would never notice it. In fact, wherever it was possible, the running time of the train was extended a few minutes, so that the delay would be only a minute or two.
After all the passenger trains had been placed on the board and the meeting-points provided for, the freight trains were added. Meeting-points with the freight trains had also to be arranged, but this was comparatively easy, as it was simply a question of the freight heading in at the last siding it could reach in advance of the passenger, and then waiting for the passenger to go by.
When every train had been placed on the board and every meeting-point provided for, the time at which every train arrived at and left every station was carefully noted down.
“And that’s done,” said Mr. Schofield, with a sigh of satisfaction. “It’s a big job, and I’m mighty glad we won’t have to do it soon again. What do you think of it?”
“It’s great,” Allan answered. “Who thought it out?”
“I don’t know. It’s been in use for a long time—practically all roads ‘string the chart,’ just as we have done. It’s the safest system that has ever been devised.”