what,” suddenly exclaimed Donald, “we’ll all go to El Paso. We’ll ride there. It isn’t so many days out of our way, and we’ll see something of the country. We might even get a look at President Madero, of Mexico.”

Donald’s suggestion met with immediate approval by the others, and so, instead of going southwest from Albuquerque, they headed south. Because of the lay of the land, they had traveled farther south than was really necessary, but had figured it out that it would be better riding in the valley of the Rio Grande than to climb over the range of mountains that forms the watershed of the Pecos River. Striking the Rio Grande near Langtry, they had slowly ridden up stream toward El Paso, first on one side of the river and then on the other, until this afternoon found them approaching the mouth of the Concho river, which empties into the Rio Grande from the Mexican side.

Two hours previous they had halted in the chaparral for a bite to eat and a short siesta. While they were lounging about, Donald had announced his intention of going to a little hamlet, the adobe houses of which could be seen a couple of miles

away, to see if he could not buy a riata, as a rope for leading horses is called.

“Why not wait until we reach Presidio?” queried Adrian. “We should reach there by dark.”

“We may not, and we need it to tether the pack mules. The one on Bray is worn out, and first thing we know he’ll wander away and we’ll waste a whole day looking for him.”

“Well, hurry up, then,” said Billie. “We don’t want to be waiting around here all the afternoon.”

Without more words Donald had mounted Wireless, for so his mount was named, and ridden away in the direction of the houses, while Billie and Adrian had strolled up the bank of the river, killing time. It was during this stroll that Billie had offered to show his skill with a six-shooter by hitting a silver dollar thrown into the air.

They had hardly been out of sight of the halting place during their stroll, but, upon their return, instead of finding Donald, they found old Bray, one of the pack mules, missing, just as Donald had predicted.

“He cannot have gone far,” declared Adrian. “He hasn’t had time.”

“That’s certain,” was Billie’s reassuring comment, and, feeling sure that a few minutes’ search of the chaparral would reveal the missing animal, they started out hastily, on foot, not deeming it necessary even to mount their steeds.

For the next ten minutes they tramped through the chaparral, calling to each other as they went, but no sign of the mule could be found. Then they returned to the camp and mounted their horses, but, although this enabled them to see over the tops of the mesquite bushes that spread out for miles up and down the river, they could see nothing of the missing animal.

“There comes Don,” Billie at last sung out, as he caught sight of the returning horseman. “Maybe he can give us some advice.”

But Donald had no advice to give, except to scatter and search.

“I hate to say 'I told you so,’” laughed Donald, “because it was really my fault that I didn’t get a new riata before. I reckon now we might as well decide to stop here all right, for I can see we have our afternoon’s work cut out.”

Half an hour’s riding having revealed no sign of Bray, the boys again met at the camp.

“Haven’t you seen anything at all?” called out Adrian, as the boys came within hailing distance of each other.

“Yes,” replied Billie, “I saw a hacienda about three miles up the river. I knew Don spoke a little Mexican, so I came back to tell him, and ask if you didn’t think it would be a good thing to apply to the owner for help. Maybe some of the peons have run across Bray and driven him home.”

“Good idea,” said Adrian. “You fellows go up to the hacienda and I’ll stay here and look after the other mule and the camp. I’m glad Bray didn’t have his pack on, or we’d stand a chance of going hungry tonight.”

“Don’t mention such a thing,” laughed Billie. “The very thought of it fills me with despair.”

CHAPTER II.—A WILD CHASE AND ITS RESULT.

The hacienda which Billie had discovered in his search for the lost pack mule was located about a mile from the Rio Grande on the Mexican side of the river, and appeared to be part of an estate of considerable size. The house itself was a good-sized dwelling, built in true Mexican style, with a great wall surrounding it, and the yard, or patio, as it is called, inside the walls. It was of dazzling whiteness, and, situated upon a little knoll that rose almost abruptly out of the otherwise level plain, made quite a pretentious appearance.

“Looks as though it might belong to people of quality,” remarked Donald, as the boys approached it, after a sharp gallop of twenty minutes.

“Yes, or a fort of some kind, with that high wall all around it.”

“The wall, as you call it, is part of the house,” explained Donald. “However, it serves the purpose of a fortification. Father told me they got into the habit of building their houses in this way

during the days when revolutions were of almost daily occurrence.”

“A habit from which they haven’t yet recovered,” laughed Billie.

Riding up to the great front door, or gate, which they found closed, they knocked loudly. A sharp-eyed Mexican lad answered the summons and ushered them into the patio, where they sat quietly upon their horses until the owner appeared. He was a little, weazened old man—Don Pablo Ojeda, by name, as the boys afterward learned—but he received them with a great show of friendliness.

“Welcome, strangers,” he said, by way of greeting. “What can I do for you today?”

“We are travelers,” replied Donald, “and one of our pack mules strayed away. Being unable to find it, we thought perhaps some of your servants might have come across it, and, not knowing to whom it belonged, have driven it to this place.”

“Quite possible,” replied the old man. “I will summon them and inquire.”

This he did. In response to his summons, half a dozen peons put in an appearance, but all denied any knowledge of the mule.

“He has probably gone down the river in the direction from which you came,” said Don Pablo, after the servants had gone back to their work. “That would be the most natural thing.”

“Quite likely,” was Donald’s reply. “We will

look for him in that direction. We are much obliged to you for your trouble.”

“No hay de que,” meaning, there is no occasion for thanks, was the Mexican’s answer, and, without more ado, the boys took their departure.

“The old hypocrite,” exclaimed Donald, as soon as the boys were out of earshot. “I actually believe he found the mule himself, and knows where he is at this very minute.”

“I thought that myself,” commented Billie, “although I could understand very little of what was being said. But he was altogether too gracious.”

“What most aroused my suspicions,” said Donald, “was a side remark I heard him whisper to that big dark peon. I didn’t get the whole of it, but it was something about removing the livestock to another pasture. But he can’t fool me, if ever I get sight of old Bray, for he had the Keystone brand.”

The boys walked their horses slowly along, talking the matter over, undecided what to do next; but, as they at last emerged from behind a long row of cactus, which formed a hedge around one side of the hacienda, Billie uttered a sudden exclamation.