Rob had stopped examining the shore upon which they were standing. He turned his gaze across the stream to the opposite bank, for his scout training told him that since the breeze came from that quarter he would be apt to learn the cause of the odor, so like burnt powder, if he followed it up.
The others heard Rob give a half suppressed shout, as though he had made a sudden and startling discovery.
"Oh! what is it?" cried Tubby, straining to keep his horse from trying to start up the ascent again.
"Across the river, over there under the arch of the bridge, don't you see that little curl of blue-white rising?" exclaimed Rob. "Watch it and you'll find that it is creeping along over the ground. Come, we've got to get up out of this in a hurry! Turn your horses, and let them help to drag you up! Quick, everybody; not a second to lose, I tell you!"
Tubby no longer tried to hold his horse back; on the contrary, he even urged the animal to climb the grade in frantic haste. He did not know what it all meant, but Rob acted as though there must be some terrible danger threatening them; and Tubby was no fool.
With cries and shouts they urged the animals to ascend. Several times a horse would slip, and come near falling headlong backward; then it was the one who held the reins found it necessary to encourage the struggling beast with word and act, so that the horse might regain his footing.
Tubby, chancing to glimpse Rob's face about the time they drew near the top was horrified to see how very white it seemed. Then more than ever did he realize that it must be something dreadful that had threatened them.
"Rob, tell us what it was all about?" Tubby managed to gasp, when, having reached the road again, they were hurrying back as rapidly as they could go, the horses helping to drag them along.
"Just this," Rob told him briefly. "They've fixed a mine there under the bridge, so as to blow it up; and we've had the narrowest escape of our lives!"