When the engineer saw the light it would be too late.
"Get the boys off the track.

I'll try to fix the lamp," Lister shouted, and started for the bridge.
The errand was not his.

Willis had lighted the lamp: moreover, one might have sent a workman, but when a job was urgent Lister went himself.

The job was urgent and dangerous.

Unless he made good speed, he would meet the train on the bridge and the cylinders of the locomotive projected beyond the edge.
The track was rough and fresh gravel rolled under his feet.