A number of the spearmen had gone forward as far as they dared on the spongy ground, and were gleefully hurling their spears at the negroes. The range was too long, however; the weapons fell short, and splashed into the water. And then Challis saw that for some distance around the tree the swamp was almost like a lake. The water was evidently several feet deep. And the terrified Tubus, clinging to the branches of the tree, were gazing with horror at the snouts of half a dozen crocodiles which formed a half circle projecting a few inches above the surface. Challis was almost as much horrified as the Tubus themselves. He knew the cunning and treacherous nature of the hideous beasts. He knew that usually they came upon their prey by stealth. It was a surprise to him to find that they were bold enough to attack men openly. It was clear that the hapless negroes were hopelessly imprisoned. In the tree they were safe, but they could not descend and attempt to swim away without the certainty of falling victims. And the cave dwellers crowding at the edge of the swamp laughed with delight at their enemies' plight and, yelled with disappointment when the weapons of the spearmen fell short. "Stop that!" cried Challis to John. "Tell them I am very angry with them for wasting their spears." John shouted to the men, who shamefacedly drew back. They felt no shame at trying to kill a helpless enemy, but dreaded the wrath of the white medicine man. "I must save the wretches," thought Challis. He meant to break the power of the Tubus if he could, for the sake of all the natives of the district; but he could not stand by and see two helpless men swallowed by these slimy monsters. It was clear that they could not save themselves. The hungry crocodile is pertinacious; he will not leave his expected prey. Some time or other the men would fall off the tree from sheer terror or weakness into the very jaws of the reptiles. Challis gazed across the swamp. The people, seeing that he did not share their merriment, fell silent, and watched him curiously. The swamp was covered in patches with aquaceous plants; there was no other tree except that in which the negroes had taken refuge. It would be useless to fire at the reptiles. Only the tips of their snouts were visible; Challis could not be sure of hitting a vulnerable part. He tried a shot, but, as he expected, it had no other effect than to startle the crocodiles for a moment; the next, when the sound had died away, their snouts bobbed up again. On the hillside behind the cave there grew a few small trees. "John," said Challis suddenly, "take some men up the hill, cut down a dozen strong young trees, strip off the leaves, and bring the trunks here as quickly as you can, with plenty of creepers." John started off with a band of men. The rest, excited at the prospect of seeing more big medicine, chattered noisily.