“I’ll say it is,” agreed Tom, as he climbed into his seat. “Our lives are apt to depend on that set more than once before we get through.”

Phil nodded, and climbed into the pilot’s seat. Dick gave the big propeller a spin, and amid the cheers of the Rangers who happened to be off duty and had gathered to see them start, they shot up into the sun-drenched atmosphere.

It was a glorious day for flying. The air was clear as crystal, and the boys had a view of the surrounding country that was nothing short of magnificent. Below them stretched and wound the silver ribbon of the Rio Grande, while far in the distance they could see the shimmer and glint of the Gulf of Mexico.

The exhilaration of flight went to their heads like wine, and as they swooped through the bracing air they shouted and sang, oblivious of the perils that in all probability awaited them. They were young and life was sweet, and the prospect of danger and adventure was a thing to be welcomed rather than dreaded.

Dick and Tom took turns at the wireless apparatus, keeping in touch with Steve and the camp as long as possible. But gradually the signals became fainter and fainter, and before long they were beyond their sending range, although they could still hear Steve.

“Can’t hear you any more,” clicked Steve, at length. “I’ll go and report to Captain Bradley. So long, and good luck.”

Now Dick and Tom exchanged their headsets for powerful field glasses, and swept the country below them for any sign of Espato and his band. They flew first to the cave from which they had rescued the two girls, but there was no sign of life about it, and indeed, they had hardly expected to find any, for the wily bandit would not be likely to use that place again after he knew that its location was known to the Americans.

However, the boys had the advantage of knowing that the bandit’s main stronghold was probably on the continuation of a line drawn from Laguna to the scene of the rescue, as the Mexicans had travelled in that direction continually after leaving American soil.

“Let’s land here and see what that cave looks like inside,” shouted Phil, and as this suited the others, too, he pointed the nose of the aeroplane downward, and they made a landing on the level plateau in front of the cave.

“Suppose you stay with the machine, Dick, and keep a sharp lookout, while Tom and I look around inside,” said Phil. “It might be a good idea to keep the engine running, so that we can make a quick getaway if we have to.”