“Here are the orders,” spoke Tom, a bit sharply, not answering the question.  “We’ll camp and have supper, and then we’ll go on and make all the distance we can after dark.”

“What, travel at night?” cried the Mexican, as if in horror at the suggestion.

“Yes; why not?” asked Tom calmly.  “They can’t see us after dark, and if we can strike off on another trail we may throw them off our track.  Surely we’ll travel after supper.”

“But it will be night—­dark—­we never work after dark,” protested Delazes.

“You’re going to this time,” declared Tom grimly.

“But the oxen—­they are not used to it.”

“Nothing like getting used to a thing,” went on the young inventor.  “They won’t mind after a rest and a good feed.  Besides, there is a moon to-night, and it will be plenty light enough.  Tell the men, Senor Delazes.”

“But they will protest.  It is unheard of, and—­”

“Send them to me,” said Tom quickly.  “There’ll be double pay for night work.  Send them to me.”

“Ah, that is good.  Senor Swift.  Double pay!  I think the men will not object,” and with a greedy look in his black eyes the Mexican contractor hastened to tell his men of the change of plans.

Tom took another look at the approaching Fogers.  Their carts were slowly crawling up the trail, and as Tom could plainly see them, he made no doubt but that his caravan was also observed by Andy and his father.

“I guess that’s the best plan to throw them off,” agreed Ned, when they were once more underway.  “But how are you going to explain to Delazes, Tom, the reason the Fogers are following us?  He’ll get suspicious, I’m afraid.”

“Let him.  I’m not going to explain.  He can think what he likes, I can’t stop him.  More than likely though, that he’ll put it down to some crazy whim of us ‘Americanos.’  I hope he does.  We can talk loudly, when he’s around, about how we want to get historical relics, and the Fogers are after the same thing.  There have been several expeditions down this way from rival colleges or museums after Aztec relics, and he may think we’re one of them.  For the golden images are historical relics all right,” added Tom in a lower voice.

The Mexicans made no objections to continuing on after supper, once they learned of the double pay, and a little later they went into camp.  A turn of the trial hid the Fogers from sight, but Tom and his friends had no doubt but what they were still following.

It was rather novel, traveling along by the light of the brilliant moon, and the boys and Mr. Damon thoroughly enjoyed it.  Orders had been given to proceed as quietly as possible, for they did not want the Fogers to learn of the night trip.

“They may see us,” Tom had said when they were ready to start, “but we’ve got to take a chance on that.  If the trail divides, however, we can lose them.”

“It does separate, a little farther on,” Delazes had said.