"Water suits me better," grumbled Ralph, nevertheless yielding the canteen to Jack. The lad drank sparingly, as did Pete and the others. Ralph, alone, of all the party, appeared not to realize how very precious even the little water that remained might become before long. Refreshed even by the small quantity they had swallowed of the tepid stuff, they remounted, and Pete clambered up upon his saddle. While his pony stood motionless beneath him, he stood erect upon the leather seat. From this elevation, he scanned the horizon on every side. Far off to the southwest was sweeping a dun-colored curtain--the departing sand-storm, but that was all. Otherwise, the desert was unchanged from its previous aspect. "Let me hev a look at thet thar compass," said Pete, resuming a sitting posture once more. Jack extended his wrist. "The compass is all right, I know," he said confidently. "And I know that we've bin hitting the right trail," declared Pete. "Last time I come this way was with an old prospector who knew this part of the country well enough to 'pick up' a clump of cactus. If that compass is right, we're headed straight." "Yes--if," put in the professor. "But are you quite sure it is?" This was putting the matter in a new light. Not one of the party was so ignorant as not to know that, in the many miles they had traveled, the deflection of the needle, by even the smallest degree, might have meant a disastrous error. "Why, I--I--how can it help being right?" asked Jack, a little uncertainly. "Which side have you been carrying your revolver on?" asked the professor. "Why, you know--on the left side," rejoined Jack, with some surprise. "And the compass on the left wrist?" "Yes. Why? Isn't it----" "No, it ain't!" roared Pete. "I see it all now, perfusser; that thar shootin' iron has bin deflectin' ther needle." "I fear so," rejoined the professor. Under his direction, Jack moved the compass into various positions, and at the end of a quarter of an hour they arrived at the startling conclusion that they had travelled perhaps many miles out of their way. The metal of the weapons Jack carried having, as they saw only too clearly now, deflected the needle. "What an idiot I was not to think of such a possibility!" exclaimed Jack bitterly. "Not at all, my boy," comforted the professor. "The same thing has happened to experienced sea-captains, and they have navigated many miles off their course before they discovered their error." "All of which, not bein' at' sea, don't help us any," grunted Pete. "Suppose now, perfusser, that you jes' figger out as well as you kin, how far wrong we hev gone." "It will be a difficult task, I fear," said the professor. "It'll be a heap difficulter task, ef we don't hit water purty soon," retorted the cow-puncher.