there were plenty of the navy’s submarines forever knocking about, and for an instant it occurred to him that it was one of these engaged in making some test and that the divers whom they had seen were members of the boat’s crew.

Then instantly he remembered the men had spoken in a foreign tongue, that they had carried a mysterious object to the trapdoor in the sewer, and that they had taken the same or a duplicate object from the sewer.

It was all inexplicable, puzzling, unfathomable.

Rawlins’ voice recalled him to the present.

“They’ve gone,” said the diver. “I want to find out who and what she is. You stay here. I’ll be away only a moment.”

As he spoke, he released Tom’s hand and with a final caution for the boy not to follow or move away, Rawlins floundered towards the submarine.

Interestedly Tom watched him. He noticed that Rawlins did not stir up the mud and then, for the first time, he discovered that the bottom was hard and sandy. Somehow all sense of fear and danger had left him. How foolish he had been, to be sure! No doubt, he thought to himself, it was

the unexpected appearance of the men and their grotesque forms which had aroused his imagination. There was Rawlins, still moving away and looking as terrible and awesome as had the others—even more so, if anything, with his proboscis-like helmet topped by its grid and the container on his shoulders giving him the appearance of being humpbacked.

He wondered how far the submarine was from where he stood. Rawlins now seemed close to it and yet he could not possibly tell whether his friend was really near to the craft or not. It was all most interesting, most baffling and most unreal and dreamlike. He wondered what Frank and Henry would think of his long silence. He wondered if they could hear him or he could hear them. Surely there would be no danger in speaking now. Even if those in the submarine heard him they could not tell whether it was some one under or above the water who was speaking. Why hadn’t he thought of that before? There never had been any danger. Of course, if these men had under-sea radio they must hear messages from those on land as well as the boys.

In that case they would never have had suspicions if they had overheard the boys’ conversation. They would never dream that others possessed the apparatus and would have assumed that the speakers were on shore. There was no danger; he was sure of it, and he was about to call to Frank when his attention was arrested by Rawlins’ actions.