Matt's lips compressed into a thin line and his eyes flashed.
"We'll have to keep a keen look-out for trouble," said he, "and dodge it, if any comes our way."
A few minutes later they were crossing the bridge over the Arizona Canal. Matt pulled out his old silver watch.
"Only sixteen minutes to one," he announced, with a note of exultation, "and we're fifteen miles on our way."
"Thirty miles to Frog Tanks and twenty to the next water," said Clip. "We ought to have brought a water-canteen, too. The heat is something fierce."
"We'll drink at the well, Clip, and pick up something to eat at the same place. We ought to be there in forty minutes, at the outside."
After they left the Black Cañon road, just beyond the bridge, Matt was in a country entirely new to him. The road was a bit cut up and sandy in places, but Clip whaled his machine along and they did a trifle better than thirty miles.
Two or three roads entered the one they were following, and they were all as well traveled. Here Matt's wisdom in bringing Clip along, even at the loss of some speed on the Comet's part, was made manifest. But for Clip, Matt might have gone astray on the wrong trail.
The boys were now in the region of big sahuara cacti, and the great trunks flashed past them as telephone-poles recede behind a rushing train.
In the dusty places of the road the broad tracks left by the tires of an automobile could be plainly seen. The red roadster was ahead of them. Matt studied the skyline in advance, wondering how far away the two ruffians were and what their designs could be. He saw nothing of the red car, and presently the square walls and flat roof of an adobe house broke on his vision.