As the crew whistled and sang the _Vulcan_ kicked a frothy course down the long westward lane. To every one's surprise, the submarine did not dive immediately, but straightened herself on the other side of the seaweed field on a course parallel with her quarry.

Madden climbed up on the bridge and found a pair of binoculars in the chart room. He took these outside and trained them on the little vessel.

Apparently the submarine intended to remain at the surface for some time, for she had opened her hatches and an officer had come out on the slender deck, and stood looking at the _Vulcan_ through a telescope.

At the distance, Madden could see the fellow plainly, and even the inky shadow he threw on the deck. The officer perused the tug for several minutes, then allowed his glass to wander around the horizon.

"They've come up for air," observed Caradoc, who had approached his friend from behind. "I believe we'd best stop that. Good air is a luxury with those fellows." He turned to Galton, who was steering. "Swing her into the northwest, my man."

The tug answered to her helm with a quiver, and in twenty minutes more was nosing her way again through the ooze of weed. The German officer calmly completed his survey, folded his telescope, then disappeared down the hatch. A few minutes later the submarine dived and the ocean lay empty in the burning sunshine.

From below came the clanging of Gaskin's gong announcing dinner. It was odd how the little details of life went calmly on even when life itself was threatened with extinction. As Madden went below to his meal, he met Malone who came from below, looking as black as an Ethiopian. The mate had been directing the firing in this extreme necessity.

The two fell in together as they walked to the wash room.

"I daresay those fellows wish they had sunk the _Vulcan_ when they had her," observed the American.

"They needed 'er theirselves," explained the mate in a matter-of-fact way. "Those German cruisers 'ave captured a whole flotilla of prizes lately, and they needed th' tug to 'andle 'em for 'em."

"And they didn't need the _Minnie B_?"

"Oh, no, not at all."

"Why didn't they sink her at once?"

"Her cap'n told me she carried more copper than one submarine could reship, so they 'ad to wait for another, as they didn't want to throw no copper away."

Madden nodded. "It was the second submarine I saw on the night she foundered." He began smiling when he thought what a bewildering mystery the vessel had been, and how very simple was the explanation.

By this time Caradoc had joined the two men, hoping to snatch a sandwich and a cup of coffee before he was needed again.

"Have we plenty of coal, mate?"

"Bunkers are 'arf full, sir."

"What's she turning over now?"

"Six, seventy-five to th' minute, sir." There was a pause, then Malone asked, "Is there any 'opes of _them_ running out o' fuel?"

"Not likely; they make the trip to Hamburg, you know."

They were just turning into the smelly galley, when a startled voice sang out forward:

"Sail ahoy!"

This stopped the trio instantly.

"Where away?" called Caradoc.

"Dead ahead, sor!"

All three turned and went running back updeck. When they regained the bridge, Madden stared in the direction indicated. At first the western horizon looked empty, then along its level line his eye caught two tiny marks against the brilliant sky. As it was too small for his naked eyes, he resorted to the binoculars once more. Caradoc was doing the same thing.

"W'ot is it, sir?" inquired Malone anxiously.

When he had focused his glasses, Madden made out two fighting tops--steel baskets circling steel masts, thrust up menacingly over the slope of the world.

"W'ot is it, sir?" repeated Malone uneasily.

Just then Madden's eye caught the flag at the peak, as it fluttered under the drive of the distant ship. It was the black cross on the white ground, with the dark upper left quarter of the German navy.

Caradoc took down his glass at the same time.

"They've been using the wireless," he stated evenly, "to run us in a _cul de sac_. I might have known German cruisers were close around." He looked steadily at the distant fighting tops, then turned to Galton.

"Steer due north, quartermaster."

After a moment, he said to Malone:

"When you go below, send me up coffee and a biscuit."

CHAPTER XX

THE LONE CHANCE

Rushing up the slope of the world in a battle line that covered a wide sector of the southwestern horizon, steamed four German battle cruisers.

They were four sea eagles dashing at a little water beetle of a tug--the hammer of Thor swinging forward to crush an insect. The submarine had signaled by wireless the whole German South Atlantic fleet to destroy the tug.

Only in the face of this demonstration did Madden realize that a great German naval stratagem hinged upon the fate of the little English boat.

The slow, clumsy little _Vulcan_ would decide the fate of millions of dollars worth of English shipping. The little vessel was freighted with huge consequences.

At first glimpse of the battle line, the _Vulcan_ had sheered about, and now rushed northward, stringing her black smoke flat behind her. Up from the south, the submarine followed on the surface, although she could not make as good time through the weed as did the _Vulcan_. However, the burden of destroying the English craft had been transferred to the cruisers that came rushing forward at at least twenty-five knots an hour.

As Madden stood on the bridge in the skirling wind, the little _Vulcan_, the seaweed drifts and the cruisers reminded him of nothing so much as a rabbit flying across cotton rows in front of four greyhounds; only here there were no friendly briar patches or fence corners in which to double or hide. Never had the Sargasso appeared so vast, so empty, so brilliant, so hot.

"Any chance?" he shouted to Caradoc above the rumble of machinery and the whistling of the wind.

"There's always a chance! They might foul in these weeds!" he nodded aft.

"Improbable."

"Lloyds would hardly insure us," admitted the commander dryly.

At that moment, as if to lend point to the remark, came a sharp clap of thunder off their port bow. Madden whirled quickly. A ball of white smoke, the size of a balloon, drifted up in the air a quarter of a mile distant.

The American stared at the smoke quite wonderstruck, then looked around at the distant ships that had not yet topped the horizon.