"That will be all right, I imagine," was the rejoinder, "but don't keep on too long. The bed of the sea, according to the chart, rises up very rapidly further on. It must be almost cliff-like in its sudden elevation."
"I'll be on the lookout," the inventor assured him.
Rob descended the ladder once more and reëntered the engine room to find out how Merritt was getting along. He found the young engineer seated on the leather lounge alongside the engines watching them lovingly.
"Work smoothly, don't they?" he said.
"They sure do," was the other's response; "smoothly as a Geneva watch."
The boys sat chatting on various matters, and the time flew along rapidly till Rob suddenly looked at his watch.
"Almost two hours. It's time we were rising," he said.
"What do we want to rise for? It's deep enough here, isn't it?"
"That's just it. The ensign says that the chart shows that a sort of submarine cliff looms up right ahead of us somewhere hereabouts."
"Great ginger snaps! I thought the bottom of the sea was as level as a floor."