The Elusive Loophole.

“But you have a lot of lines in this yard. Could not a head-on collision occur?”

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“No. Again the points are so arranged that trains travelling in different directions on the one line would be carried to safety on different lines upon reaching the points.”

I saw my chance and leapt to it like a tiger.

“That is all very well for double tracks, Mr. Signalman, but what about a Single track?”

My companion did not blink an eyelid. For a moment I pitied him. Then I pitied myself, because he said: “The automatic system divides the railway line into sections of quarters of a mile. That system serves the Hutt. Upon a train entering a section it automatically places the signals at both ends of the section at danger. That holds up a train that may be waiting at either end to come on, thus preventing collision in the front or at the back. Opposing trains then cross on a loop line at the end of the section at which they meet.”

I felt I was playing a game of draughts and was losing all my men. However, I perceived what I thought was a loophole.

“That is a safeguard which applies only to the electrified railway,” I said. “The Palmerston North line is not electrified. How about the danger of collision on that?”

“Ah, there we operate on the tablet system.”

I had an idea of what he meant. Tablets were those composition discs that engine-drivers exchanged with signalmen at stations, not unlike the pleasant swopping of cigarette cards. It had always appeared to me to be a happy and aimless pastime, bound up with the curious legend I had heard that no driver would travel without his disc. I was to learn why.