Without a word they departed on their quest, and Mackay and Bob were left alone. Calmly the elder man interrogated the lad, who was standing in an attitude of deepest dejection, the sextant hanging loosely in his hand.
"And is there no room for a mistake in any o' your figures, Bob?"
"None, none, that I can imagine. I have been particularly careful——"
Bob could not finish his sentence, a flood of emotion swept over him, and he sat down in the sand and covered his face with his hands.
"Why, my laddie, ye mustn't blame yoursel' for no error o' yours," spoke Mackay, kindly, gazing at the despondent youth with a strange light in his keen grey eyes. "Brace yoursel' up, Bob; we'll likely find the spring at no great distance, an' if we don't, well—we'll look for another one if the camels stand by us."
He hurried away into the eastward scrub. Bob arose and gazed after him with quivering eyelids.
"Yes," he murmured brokenly, "I have brought you all to your death, and I can do nothing now to save.... I know the error is not mine, but I cannot and will not blame a dead man.... I wonder what can possibly be wrong."
He shook his head in utter hopelessness, then he glanced at the sextant, lying as he had left it, half buried in the sand. He took it up and brushed the silvered arc carefully with the ragged sleeve of his shirt, and was preparing to place it in its case when a new idea seemed to strike him. He grasped the instrument with a firmer grip and stood erect, a new light, a light of gladness shining in his eyes.
"It's strange I never thought of it before," he said aloud; "a minute or two either way would make all the difference." He picked up the chronometer, which lay idly at his feet, and examined it critically. "It's just possible," he muttered, "the jolting of the camel may have made it go a bit fast; I wonder if I can check it. I am going to try."
Long and eagerly he gazed at the sun through the powerful telescope of the sextant, and every now and then he would note down his observations, and consult the Nautical Almanac which lay open before him. In the midst of these proceedings, Emu Bill and Never Never Dave returned, after a fruitless search, and while they stood watching him, Jack and the Shadow also made their appearance, and lined up beside the other two in solemn silence. There was no need to ask them if they had been successful, their faces plainly indicated disappointment, though they both strove hard to hide their feelings. As for the first arrivals, their rugged countenances betrayed not the slightest trace of emotion. Bill calmly chewed a quid of tobacco, and Dave reflectively pulled at his pipe. To them it did not seem to be a matter of much moment whether they found the spring or not. At length Bob threw down the sextant with a weary sigh.