Still waving the wandering beam of white light, the flag-ship passed on, bringing along the second in line, and again Metcalf turned on his bulb.

He heard her bugle-call, and saw, in varied shades of green, the twinkling red and blue lights of her masthead signals, received from the flag-ship and passed down the line. And again he played that green disk of deadly light upon the faces of her crew. This ship, too, was seeking him with her searchlight, and soon, from the whole nine, a moving network of brilliant beams flashed and scintillated across the sky; but not one settled upon the cause of their disquiet.

Ship after ship passed on, each with its bugle-call to quarters, each with its muster of all hands to meet the unknown emergency--the menace on a hostile coast of a faint white light on the port beam--but not one firing a shot or shell; there was nothing to fire at. And with the passing of the last of the nine Metcalf listened to a snapping and a buzzing overhead that told of the burning out of the carbons in the light.

"Good work for the expenditure," he murmured, wearily. "Let's see--two carbons and about twenty amperes of current, against nine ships at ten millions apiece. Well, we'll soon know whether or not it worked."

While an electrician rigged new carbons he rested his eyes and his brain; for the mental and physical strain had been severe. Then he played the light upon the colliers and supply ships as they charged by, disposing of them in the same manner, and looked for other craft of larger menace. But there were none, except the torpedo contingent, and these he decided to leave alone. There were fifteen of them, each as speedy and as easily handled as his own craft; and already, apprised by the signaled instructions from ahead, they were spreading out into a fan-like formation, and coming on, nearly abreast.

"The jig's up, chief," he called through a tube to the engineer. "We'll get forty feet down until the mosquitoes get by. I'd like to take a chance at them but there are too many. We'd get torpedoed, surely."

Down went the diving rudder, and, with a kick ahead of the engine, the submersible shot under, heading on a course across the path of the fleet, and in half an hour came to the surface. There was nothing in sight, close by, either through the periscope or by direct vision, and Metcalf decided to make for San Francisco and report.

It was a wise decision, for at daylight he was floundering in a heavy sea and a howling gale from the northwest that soon forced him to submerge again for comfort. Before doing so, however, he enjoyed one good look at the Japanese fleet, far ahead and to port. The line of formation was broken, staggered, and disordered; and, though the big ships were making good weather of it, they were steering badly, and on one of them, half-way to the signal-yard, was the appeal for help that ships of all nations use and recognize--the ensign, upside-down. Under the lee of each ship was snuggled a torpedo-boat, plunging, rolling, and swamped by the breaking seas that even the mighty bulk to windward could not protect them from. And even as Metcalf looked, one twisted in two, her after funnels pointing to port, her forward to starboard, and in ten seconds had disappeared.

Metcalf submerged and went on at lesser speed, but in comfort and safety. Through the periscope he saw one after the other of the torpedo-craft give up the fight they were not designed for, and ship after ship hoist that silent prayer for help. They yawed badly, but in some manner or other managed to follow the flag-ship, which, alone of that armada, steered fairly well. She kept on the course for the Golden Gate.

Even submerged Metcalf outran the fleet before noon, and at night had dropped it, entering the Golden Gate before daylight, still submerged, not only on account of the troublesome turmoil on the surface, but to avoid the equally troublesome scrutiny of the forts, whose searchlights might have caught him had he presented more to their view than a slim tube painted white. Avoiding the mines, he picked his way carefully up to the man-of-war anchorage, and arose to the surface, alongside the _Delaware_, now the flag-ship, as the light of day crept upward in the eastern sky.

"We knew they were on the coast," said the admiral, a little later, when Metcalf had made his report on the quarter-deck of the _Delaware_. "But about this light? Are you sure of all this? Why, if it's so, the President will rank you over us all. Mr. Smith came in with the prisoners, but he said nothing of an invisible light--only of a strong searchlight with which you set fire to the signal-yard."

"I did not tell him all, admiral," answered Metcalf, a little hurt at the persistence of the feeling. "But I'm satisfied now. That fleet is coming on with incompetents on the bridge."

"Well, we'll soon know. I've only one ship, but it's my business to get out and defend the United States against invaders, and as soon as I can steam against this gale and sea I'll go. And I'll want you, too. I'm short-handed."

"Thank you, sir. I shall be glad to be with you. But wouldn't you like to examine the light?"

"Most certainly," said the admiral; and, accompanied by his staff, he followed Metcalf aboard the submersible.

"It is very simple," explained Metcalf, showing a rough diagram he had sketched. "You see he has used my system of reflectors about as I designed it. The focus of one curve coincides with the focus of the next, and the result is a thin beam containing nearly all the radiations of the arc."

"Very simple," remarked the admiral, dryly. "Very simple indeed. But, admitting this strong beam of light that, as you say, could set fire to that sealer, and be invisible in sunshine, how about the beam that is invisible by night? That is what I am wondering about."

"Here, sir," removing the thick disk from around the light. "This contains the prisms, which refract the beam entirely around the lamp; and disperse it into the seven colors of the spectrum. All the visible light is cut out, leaving only the ultraviolet rays, and these travel as fast and as far, and return by reflection, as though accompanied by the visible rays."

"But how can you see it?" asked an officer. "How is the ship it is directed at made visible?"

"By fluorescence," answered Metcalf. "The observer is the periscope itself. Any of the various fluorescing substances placed in the focus of the object-glass, or at the optical image in front of the eyepiece, will show the picture in the color peculiar to the fluorescing material. The color does not matter."

"More simple still," laughed the admiral. "But how about the colored lights they saw?"

"Simply the discarded light of the spectrum. By removing this cover on the disk, the different colored rays shoot up. That was to attract attention. I used only white light through the periscope."

"And it was this invisible light that blinded so many men, which in your hands blinded the crews of the Japanese?" asked the admiral.

"Yes, sir. The ultraviolet rays are beneficial as a germicide, but are deadly if too strong."

"Lieutenant Metcalf," said the admiral, seriously, "your future in the service is secure. I apologize for laughing at you; but now that it's over and you've won, tell us about the spectacles."

"Why, admiral," responded Metcalf, "that was the simplest proposition of all. The whole apparatus--prisms, periscope, lenses, and the fluorescing screen--are made of rock crystal, which is permeable to the ultraviolet light. But common glass, of which spectacles are made, is opaque to it.

That is why near-sighted men escaped the blindness."

"Then, unless the Japs are near-sighted, I expect an easy time when I go out."

But the admiral did not need to go out and fight. Those nine big battle-ships that Japan had struggled for years to obtain, and the auxiliary fleet of supply and repair ships to keep them in life and health away from home, caught on a lee shore in a hurricane against which the mighty _Delaware_ could not steam to sea, piled up one by one on the sands below Fort Point; and, each with a white flag replacing the reversed ensign, surrendered to the transport or collier sent out to take off the survivors.

IN THE VALLEY OF THE SHADOW

There are few facilities for cooking aboard submarine torpedo-boats, and that is why Lieutenant Ross ran his little submarine up alongside the flag-ship at noon, and made fast to the boat-boom--the horizontal spar extending from warships, to which the boats ride when in the water. And, as familiarity breeds contempt, after the first, tentative, trial, he had been content to let her hang by one of the small, fixed painters depending from the boom; for his boat was small, and the tide weak, bringing little strain on painter or boom. Besides, this plan was good, for it kept the submarine from bumping the side of the ship--and paint below the water-line is as valuable to a warship as paint above.

Thus moored, the little craft, with only her deck and conning-tower showing, rode lightly at the end of her tether, while Ross and his men--all but one, to watch--climbed aboard and ate their dinner.

Ross finished quickly, and sought the deck; for, on going down to the wardroom, he had seen among the visitors from shore the one girl in the world to him--the girl he had met at Newport, Washington, and New York, whom he wanted as he wanted life, but whom he had not asked for yet, because he had felt so sure of her.

And now this surety was jolted out of his consciousness; for she was there escorted by a man she had often described, and whom Ross recognized from the description--a tall, dark, "captainish"-looking fellow, with a large mustache; but who, far from being a captain or other kind of superman, was merely a photographer--yet a wealthy and successful photographer, whose work was unusual and artistic.

Ross, though an efficient naval officer, was anything but "captainish"; he was simply a clean-shaven, clean-cut young fellow, with a face that mirrored every emotion of his soul. Knowing this infirmity--if such it is--he resolutely put down the jealous thoughts that surged through his brain; and when the visitors, guests of the captain, reached the deck, he met them, and was introduced to Mr. Foster with as pleasant a face as the girl had ever seen.

Then, with the captain's permission, he invited them down to inspect his submarine. A plank from the lower grating of the gangway to the deck of the smaller craft was all that was needed, and along this they went, the girl ahead, supported by Mr. Foster, and Ross following, with a messenger boy from the bridge following him.

At the hatch, the girl paused and shrank back, for the wide-open eyes of the caretaker were looking up at her. Ross surmised this, and called to the man to come up and get his dinner; then, as the man passed him and stepped onto the plank, the messenger got his attention. The officer of the deck desired to speak with him, he said.

Ross explained the manner of descent, admonished his guests to touch nothing until he returned, and followed the messenger back to the officer of the deck. It was nothing of importance, simply a matter pertaining to the afternoon drill; and, somewhat annoyed, Ross returned.

But he paused at the end of the plank; a loud voice from below halted him, and he did not care to interrupt. Nor did he care to go back, leaving them alone in a submarine.

"I mean it," Foster was saying vehemently. "I hope this boat does go to the bottom."

"Why, Mr. Foster!" cried the girl. "What a sentiment!"

"I tell you I mean it. You have made life unbearable."

"I make your life unbearable?"

"Yes, you, Irene. You know I have loved you from the beginning. And you have coquetted with me, played with me--as a cat plays with a mouse.

When I have endeavored to escape, you have drawn me back by smiles and favor, and given me hope. Then it is coldness and disdain. I am tired of it."

"I am sorry, Mr. Foster, if anything in my attitude has caused such an impression. I have given you no special smiles or favors, no special coldness or disdain."

"But I love you. I want you. I cannot live without you."

"You lived a long time without me, before we met."

"Yes, before we met. Before I fell under the spell of your personality.

You have hypnotized me, made yourself necessary to me. I am heartsick all the time, thinking of you."

"Then you must get over it, Mr. Foster. I must think of myself."