Jim rubbed his eyes; the sudden change in the movement of progression of the launch amazed him. He could hardly believe that she was retreating, that those agitated ripples now spreading from her stern right forward beyond the bows meant that she was departing. It was the whirr of her engine and the splashing of her propeller as it churned the water violently which brought the true facts clearly to his mind. "They're off," he shouted; "we must follow. Quick, on to the launch!" He dashed along the bank of the stream, calling loudly to the men, and arriving opposite to their own vessel, swiftly cast adrift the rope which had been passed from her stern to a tree growing close down to the water. With a spring he was aboard, and, tumbling at once into the well, he searched in the darkness for the starting handle. But however convenient a gasolene motor may be on ordinary occasions, the fact cannot be denied that there are at times difficulties in connection with them. For instance, it was always a practice of Jim's to shut off his petrol supply when the engine was not running; for otherwise there was risk of leakage through the carburettor, and leakage of such a volatile and inflammable fluid aboard a boat spells danger for those who man her. Then, too, it happened that this engine trusted to drip lubricators for her supply of oil, and though she might reasonably be expected to run satisfactorily for a while without that supply, still, in the exciting time before him, Jim might easily forget to turn up his lubricators, and such neglect spelt failure for his party. After all, this was decidedly one of those cases where it would be better to follow his usual routine, and thereby make sure that the engine had everything in its favour. "I'll have her running in double-quick time," he shouted. "Get that painter cast off, Major; and, see here, can't you manage to push her along until I have got the engine going?" "Guess I'se got one mighty big pole here," called Tom, an instant later, whilst the launch heaved and rolled as the ponderous fellow moved about. "You get right along wid dat engine, Massa Jim. I'se gwine astern to pole her." Once more the launch rolled and heaved as Tom made his way rapidly aft. Then his pole plunged into the water, one of the policemen pushed the bows out from the bank, and, casting his eye upward for one brief instant, Jim saw that they were moving. Meanwhile he had found the gasolene tap and turned it, while the fingers of his other hand as rapidly lifted the six lubricators which fed the engine with that fluid so vital to her. "Ready?" asked the Major tersely, his voice hard and cold, as if sudden disappointment had changed it. "Get her going quick, my lad, or those fellows will get clear away from us. Already they are steaming right out into the lagoon."