Together the posse rode on, making a trail back to the main defile, and out of the one down which the Greaser and his gang had turned, where they had been discovered by Dick. And then Bud's prediction came true. The sun, which never shone directly into the main canyon for any great length of time, began to set, bringing gloom into the defile long before it would make its appearance on the level country up above. Seeing the gathering darkness, Slim advised calling a halt, and this was done several miles beyond the place where the last trace of the stolen cattle had been observed. "Shall we camp here!" asked Bud, deferring to the foreman, as was natural under the circumstances. "We've got grass and water," Slim remarked, indicating a spring toward which, even then, some of the horses were hastening. "Water for the ponies and us, grass for the animals, and there ought to be some grub left." "There is," said Snake Purdee, who had assumed, or been given (it did not much matter which) the office of commissary. "We brought along plenty." "And we may need it before we reach the end of the trail," remarked Bud. "I don't believe it's going to be easy to find where those cattle disappeared to." "There's only two ways, or at th' most three, in which they could be kept away from us," said Slim, as he slid from his saddle. "What are they?" asked Dick, who, like his brother, was always eager to learn from a true son of the West, such as was the foreman of Diamond X. "Well," Slim resumed, "they've either been driven down some side passage, or gorge, such like as we found Del Pinzo in, or they were back-tracked to th' open an' driven off there th' same night they was run off." "That might be," admitted Bud. "I didn't think of a back track." "Well, I did," Slim said, "but the signs of it was so faint I passed it up." A back trail, I might explain, is where an animal, or several of them, or even a human, for that matter, turns and retraces the way first traveled. A fox, fleeing before the hounds, will often do this, and as the scent does not indicate the direction in which Reynard is running, the dogs are often deceived. But in the case of the fox the imprints of the animal's paws are so light that perhaps only with a microscope could it be told when he had "back-tracked." Except, of course, in some place where soft mud might retain the impression of both trails. In the case of a large body of cattle, also, though the scent would not be relied upon, it would be difficult for the casual, or, in some cases, even the trained observer, to say where the herd had been turned and driven back over the same course originally taken. Thus pursuers would be baffled. And when to this is added the fact that the floor of the gorge was of rock, in the main, which did not take, or retain, any impressions, the puzzle was all the more difficult to solve. "Well, we'll see what happens in the morning," observed Bud, as preparations for the camp went on.