The old trail had never been used for wagons, but had been exclusively given over to pack-burros. Consequently it was narrow, and there were places where bunches of cactus grew so close that the boys had to leave their saddles and trundle their machines past by hand, in order to keep the sharp spines from puncturing the tires.
When the cactus bunches ceased to bother, the pack-trail swung into rocky ground, and the boys had to do some hair-raising stunts in following a bit of shelf with a sheer drop of thirty or forty feet on one side of them and a straight up-and-down wall on the other.
At last the trail climbed over a ridge and into easier ground. Huge piles of rocks flanked both sides of the way, but the going was smooth and level.
While they were passing through this strip of country, Matt suddenly heard voices behind him and to the left of the trail. The voices came from a considerable distance, and were muffled and indistinct, but Matt heard them plainly enough.
"Chub!" he called in a guarded tone, "ride around that pile of rocks on the left. Some one's coming behind us and we'd better wait and see who it is."
Without pausing to ask any useless questions, Chub swerved from the trail and guided his motor-cycle around the heap of boulders referred to by Matt. Matt followed him, and they screened themselves and their wheels as well as they could and peered curiously back along the trail.
[CHAPTER VIII.]
TOO LATE!
As the boys breathlessly watched, they saw a burro emerge from among the rocks on the left of the trail. There was no load on the burro's back, and the shaggy little animal was being driven by two ruffianly-looking men. One of the men had a club, and every once in a while he would reach over and hit the burro a heavy blow. The burro would flinch and leap ahead; then, apparently forgetting what had happened, would lag again and the blow would be repeated.