The colonel rose, and going down to the canoe helped himself to a handful of crackers and some figs. He came back to his seat and began to munch them very contentedly.

“The most merciful thing we could do would be to cast our provisions into the lake,” he said finally. “It would cut short the agony of waiting, but I don’t suppose you would look at it in that way.”

“No, no; don’t do that,” cried Chutney. “Who knows what may happen yet?”

“Ah! there you are again,” said the colonel; “still clinging to hope of life; still unable to realize the truth. You are only making it so much the harder for yourself.”

“But there is surely some outlet to this vast body of water?” said Melton.

“Yes,” was the colonel’s reply. “Undoubtedly, but it must be at the bottom of the lake; it certainly is not on the surface. Do you suppose those poor savages would have perished here if an outlet had existed? They, too, must have been carried by accident into the wrong channel, and no doubt they circumnavigated the lake, as we have done. Realizing that they were lost, they either slew themselves to end their sufferings or they fell victims to the serpents without much resistance.”

While Melton and the colonel were carrying on this conversation, Guy rose and went down to the water, with the intention of gathering some food, for he, too, was hungry.

The canoe was pulled partly on shore, and as it leaked a little the water had all collected in the stern, where Sir Arthur still lay in merciful sleep, thus wetting the rugs.

Guy noticed this, and with a view to making the sleeper more comfortable, he slid the canoe down until it lay flat in the water. It still retained a slight hold of an inch or two on the sand.

A sudden cry from the Greek brought him back in a hurry to the top of the island.

His companions were staring out on the lake, and Canaris was pointing with a trembling hand at some unseen object.

“What is the matter?” cried Guy. “What do you see?”

“Hush,” said the colonel, holding up a warning finger. “Something is moving out on the lake. Do you hear it splashing in the water?”

As yet nothing could be seen, but the noise was very plain and distinct, a steady swish! swish! not unlike the beating of a little steamer.

A chilling fear grew on them as they listened to this strange, mysterious sound.

“Whatever it is, it is moving in a circle round the island,” said Guy, “and keeping an equal distance from the shore.”

“You are right, Chutney,” said the colonel, after a pause. “The sound was on our left a moment ago. Now it is on our right.”

The Greek was correct. The surface of the lake was violently agitated, though not a breath of air was stirring, and a steady flow of ripples was breaking on the sandy beach like tiny ocean waves.

The unknown navigator, whatever it was, had nearly completed the circuit of the island now, and was very near the spot where they had first heard it.

“It must be a serpent,” cried Guy. “Heaven grant that it doesn’t approach the island.”

He hurriedly picked up the torch and ran with it to the shore. The radius of light thus thrown over the water illumined a space twenty yards ahead, and revealed a long, dark object moving in graceful undulations over the surface. It was beyond doubt a huge serpent, and, as though angered by the light, the monster suddenly changed its course, and with a terrific splash headed directly for the shore. The huge head was in plain view, and the eyes flashed back fire from the reflected glare of the torch.

For an instant all seemed paralyzed with horror, and no one moved.

Chutney was the first to recover himself.

“We must kill him before he reaches the island,” he cried, staggering back a pace or two. “Get the guns. Quick! quick! or it will be too late!”

He turned to flee across the island toward the canoe, but as he gained the ridge a cry of horror broke from his lips, and as his companions hurriedly reached the spot a single glance showed them what was the matter.

The canoe was no longer on the shore. The swell caused by the approach of the serpent had washed it from its slight support, and now it was twenty yards distant, and drifting farther and farther away with every second.

“The guns! The guns!” shrieked Chutney. “They are all in the boat. We are left at the mercy of the serpent. Sir Arthur! Sir Arthur!” he shouted with all his might, but no response came from the sleeping man, and the canoe continued to recede into the gloom.

At this terrible moment it was Forbes who brought a ray of hope into their despair.

Springing forward he snatched up an armful of the native weapons, spears, and axes, and distributed them to his companions.

“We must fight the monster with these,” he cried; “and while we are keeping him off, you, Canaris, run to the shore and keep on shouting to Sir Arthur. He may wake and get here in time to save us yet.”

“He must be in a faint,” exclaimed the colonel, “or the noise would surely have wakened him. Come on, Chutney, the serpent is halfway to the shore. We may keep him off with these arms.”

The torch was hastily placed in the sand near the water’s edge, and, grasping their weapons firmly, they prepared to check the advance of the monster. Fortunately the spears and axes were of hard iron and fitted with strong handles which the long storage in the cavern seemed to have toughened.

Meanwhile the air echoed with the Greek’s loud cries, but at that moment none thought of Sir Arthur or of the canoe, for the serpent was within half a dozen yards of the island and his great body was undulating through the water for thirty feet behind him.

“Keep cool,” said Chutney. “Aim well for the head and make every stroke tell.”

The sight of the glaring eyes and the blood-red fangs was enough to appall the stoutest heart. They shrank back in uncontrollable fear, as the long neck rose four feet in air and the body sank under the water.

The monster uttered an angry hiss, but before he could spring Forbes cast a spear with all his might and the sharp point pierced the serpent’s body a foot below the head.

“Back for your lives,” he cried, and as they darted up the island the monster uttered a fearful sound, part hiss, part bellow, and flung half his length in contortions on the sand.

Guy sprang forward and launched another spear that entered the slimy body near the center, but neither wound was mortal and the great serpent came on unchecked.

In one respect they had the advantage of him, as Guy accidentally discovered, for the wicked eyes blinked in the torchlight and the monster’s actions showed that his powers of sight were limited to darkness.

He was wonderfully quick and agile, however, for a sudden convulsive leap carried him almost to the feet of his antagonists, and again they scattered in alarm.

The serpent’s whole body was now on shore, with the exception of the tail, which was lashing the water to a milky foam.

Seizing another spear Guy circled to one side, and boldly approaching the trembling coils, with one terrific blow he planted his weapon into the serpent’s body so deeply that the spear pinned the monster firmly to the ground.

A cry of horror burst from his companions as the huge head swung round with awful quickness, but it missed Guy by barely an inch as he sprang aside.

The serpent’s contortions were now frightful to see, as he squirmed and twisted to tear loose from the weapon. “Now let him have it,” cried Guy; and in an instant the remaining spears, half a dozen in number, were driven deeply into the venomous coils.

The struggle was now at its crisis. With axes in hand they were dodging about the writhing monster, seeking a chance to reach the head, when an awful shriek echoed through the cavern, apparently from some distance out on the lake, and then the Greek’s voice was raised in a loud and urgent appeal for help. What new disaster threatened?