Nor was this all. Only one man knew the route, and years had gone by since he had last travelled over it. If his strength or memory failed, it might well happen that the dreary desert would be our burial-place and the loose sand our winding-sheet. It was not exactly a cheering prospect, but we made the best of it. The colonel marched at the head of his men, the doctor at the rear, so that he might assist any unfortunate stragglers, while Jose and I went forward with the guide. With frequent halts for rest we ploughed our way through the shifting sand, our eyes aching and our throats terribly dry. About midnight, as near as I could judge, the guide stopped irresolutely. "What is it?" asked Jose, in an excited whisper; "what is wrong?" We could not see the fellow's face, but he seemed very agitated, and there was a break in his voice as he answered,-- "I don't know--I am not sure--but I can't be certain that we are on the right track." The words sounded like a sentence of death, and I could hardly repress a cry of horror. "Be still!" whispered Jose; "the men must not know. Stay here a minute while I ask the colonel to halt. That will give us a little breathing-space." He was soon back, and taking the guide's arm, he exclaimed,-- "Now come, get your wits about you, and let us see what can be done. Where do you think we ought to be?" "I don't know," replied the guide helplessly. "The saints preserve us, or we are lost!" "Now look here," said Jose sternly: "you are giving way, and that won't do. Pluck up your courage, man, and remember that all our lives are in your hands." I think, perhaps, this awful responsibility had much to do with breaking the guide down. He wrung his hands and groaned, saying aloud that he had brought us to death. "But we aren't dead yet," I remarked, "and needn't be if only you will collect your wits. Come, let us cast about a bit; maybe you'll find some landmark that will help you." "No, no," he cried; "we may be right now, and if we stray away we shall certainly be lost. May the saints preserve us!" I think the fellow would be there yet, but for the click of Jose's pistol and the stern ring in his voice as he said sharply,-- "This nonsense has to stop.--Take his arm, Jack.--Now go on without a word, until you can make up your mind one way or other about the route." The next quarter of an hour was one of the worst in my life. The man stumbled this way and that, now going in a straight line, again turning to right or left, and all the time the troops in our rear were resting in fancied security. I shuddered to think what would happen if the guide failed to locate the track. Suddenly he ran forward quickly, dragging me with him, and then uttered a joyful cry. We were at the foot of a sandy hillock of peculiar shape, much like, as far as I could tell, a truncated cone. It was not high, but apparently of considerable circumference.