As soon as it stopped he pulled a lever and a heavy steel sheet slid over the opening where the glass dome had been. In front of him as he stood at the steering-wheel was a long, very slender needle hung with extreme delicacy on a pivot, up which an electric current constantly passed.
This needle was terrestrially insulated by a magnet which always swung opposite to the magnetic pole, and when acted upon only by the steel of the vessel’s fabric, swung indifferently as long as there was no other vessel within a thousand yards of the Narwhal. But the moment one came within that distance the needle pointed towards it with unerring accuracy, as it was doing at the present moment.
Alexis allowed the vessel to back until he saw the needle begin to waver. Then he knew that the thousand-yard limit had been reached, and signalled—
“Full speed ahead.”
The next moment the engines were reversed and the Narwhal bore down on her invisible prey. The needle became rigid again. Alexis kept it pointing dead ahead as the Narwhal gathered way and rushed silently but with irresistible force upon her victim.
She passed over the thousand yards in forty seconds. Then came a dull, rending crash, a slight shiver of the mighty fabric, and then she swept on her way as though she had passed through a couple of inches of planking instead of the steel hull of a submarine warship more than two-thirds her own size.
And so in silence and darkness, without the discharge of a gun or the flash of a shot or an audible cry of human pain, the work of death and destruction began and ended. In the passing of an instant a warship had been destroyed which could have annihilated a fleet of modern battleships in detail without once appearing above the surface of the water.
The moment that the shock told Alexis that the ram of the Narwhal had done its work, he signalled “Stop,” and as the vessel slowed down he watched the momentous fluctuations of the needle in front of him. It oscillated for an instant and then became still again, pointing to another victim hidden away somewhere under the dark waters. He brought the vessel round until it pointed ahead again, and then once more the leviathan plunged forward at full speed on her errand of destruction.