"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.