"More will come," said Obed. "Just as one swallow does not make a summer, one stone does not make a flight. Ah, there it is now!" They heard that same rushing sound through the air, and a bowlder weighing at least half a ton struck in front of their log. It did not bound away like the first, but being so much heavier buried half its weight in the earth and lay there. Obed chuckled and regarded the big stone with an approving look. "It's an ill stone that doesn't fall to somebody's good," he said. "That big fellow is squarely in the path of anybody who advances to attack us, and adds materially to our breastwork. If they'll only drop a few more they'll make an impregnable fortification for us." The third came as he spoke, but being a light one rolled away. The fourth was also light, and alighting on the big one bounded back into the alcove, striking just between Ned and Obed. It made both jump and shiver, but they knew that it was a chance not likely to happen again in a hundred times. The bombardment continued for a quarter of an hour without any harm to either of the two, and then the silence came again. Ned and Obed pushed the rock out of the alcove, leaving it in front of them and now their niche had a formidable stone reinforcement. "They'll be slipping up soon to look at our dead bodies," whispered Obed, "and between you and me, Ned, I think there will be a great surprise in Mexico to-day." They lay almost flat and put the muzzles of their rifles across the log. Both, used to life on the border, where the rifle was a necessity, were fine shots and they were also keen of eye and ear. They waited for a while which seemed interminably long to Ned, but which was not more than a quarter of an hour, and then he heard a slight movement among the trees somewhat to their left. He called Obed's attention to it and the man nodded: "I hear it, too," he whispered. "Those investigators are cautious, but they'll have to come up in front before they can get at us, and then we can get at them, too. We'll just be patient." Ned was at least quiet and contained, although it was impossible to be patient. They heard the rustling at intervals on their right, then it changed to their front, and he saw a black head, covered with a sombrero, peep from behind a tree. The head came a little farther, disclosing a shoulder, and Obed White fired. They heard a yell of pain, and a thrashing among the bushes, but the sound rapidly moved farther and farther away. "That fellow was stung badly," said Obed White with satisfaction, "and he won't come back. I'm glad to see, Ned, that you held your fire, keeping ready for any other who might come." Ned glowed at the compliment. He had cocked his rifle, and was ready but he remained cool, wasting no shot.