“I know what the senors fear—­that their language may be listened to, but I assure you that this man understands no English, do you, Josef?” he asked the man in question, using the Spanish.

The man shook his head, but a quick look passed between him and his employer.

“Oh, I guess we’ll let Rad drive,” insisted Tom calmly, “it will remind him of his mule Boomerang that he left behind.”

“As the senor will,” Delazes had replied with a shrug of his shoulders, and he turned away.  So it was that Tom, Ned and Mr. Damon, in their own cart, piloted by the colored man, were in the rear of the little cavalcade.

“Have you any idea where you are going, Tom?” asked Ned, after they had reached the shade, when it was not such a task to talk.

“Oh, I have a good general idea,” replied the young inventor.  “I’ve studied the map Mr. Illingway sent, and according to that the city of—­well, you know the place we’re looking for—­lies somewhere between Tampico and Zacatecas, and which the plain of the ruined temple which used to be near the ancient city of Poltec, is about a hundred and fifty miles north of the city of Mexico.  So I’m heading for there, as near as I can tell.  We ought to fetch it in about a week at this rate.”

“And what are we to do when we get there?” inquired Mr. Damon.  “If we keep on to that place where the images are to be found, with this rascally crew of Mexicans, there won’t be much gold for us.”  He had spoken in low tones, though the nearest Mexican cart was some distance ahead.

“I don’t intend to take them all the way with us,” said Tom.  “When I think we are somewhere near the temple plain I’m going to make the Mexicans go into camp.  Then we’ll put the balloon together and we four will go off in that.  When we find what we’re looking for we’ll go back, pick up the Mexicans, and make for the coast.”

“If the head-hunters let us,” put in Ned grimly.

“Bless my nail file!  There you go again!” cried Mr. Damon.  “Positively, Ned, you get on my nerves.”

“Yais, Massa Ned, an’ I jest wish yo’ wouldn’t mention dem head gen’men no mo’,” added Eradicate.  “I can’t drive straight when I hears yo’ say dem words, an’ goodness knows dese oxes is wusser t’ drive dan my mule Boomerang.”

“All right I’ll keep still,” agreed Ned, and then he and Tom, together with Mr. Damon, studied the map, trying to decide whether or not they were on the proper trail.

They made a good distance that day, and went into camp that night near the foot of some low hills.

“It will be cooler traveling to-morrow,” said Tom.  “We will be up higher, and though we’ll have to go slower on account of the up grade, it will be better for all of us.”

They found the trail quite difficult the next day, as there were several big hills to climb.  It was toward evening, and they were looking for a good place to camp for the night, when Delazes, who was riding in the first cart, was observed to jump down and hasten to the rear.