Be watchful--that is the vital thing.

And especially so when you begin to descend a long hill.

At the bottom of that hill the railway crosses your road, and that culvert will be watched with especial care.

After that you will find the way clear, for our nearest outposts should not be more than a mile or so beyond the railway there.
We would have seized the line before, except that until we had straightened our front in that quarter it would have been useless to do it." The whistle that they heard warned them that they were getting near to this dangerous stretch of road, and in a few moments the sight of a train, sparks flying from the smokestack of the engine, gave them visual proof as well.

Then for a time they ran along parallel with the tracks.
Fires were burning along the railway at intervals of about a hundred and fifty yards, and at times, in the firelight, they could see a dark figure moving slowly.
"Heaven knows what this bugle means!" said Fred, as they drew into line with the tracks.