Jack gave the necessary command, and the D-16 slowed down perceptibly.

For many minutes there was intense silence, broken at last by Lord Hastings.

“I should say,” he said, “that we must now be in the harbor. I am positive we have passed under the mines safely.”

“Then shall we go up, sir?” asked Frank eagerly.

Lord Hastings hesitated for a moment, and then replied:

“Yes, we may as well.”

Jack took this as a command, and gave the necessary order.

Slowly the D-16 began to rise.

Lord Hastings glanced at his watch.

“Seven o’clock,” he said quietly, “and there should be no moon. A good night for our work.”