wheezing, coughing, shaking in every plate, vomiting into the sky a trail of smoke that extended clear to the eastern horizon, the vulcan shouldered her way at top speed across the mazy lanes of the sargasso. the tug had come a queer crooked path across that sea, and the lay of her smoke trail down the pearly glow of dawn still marked her tortuous course.

not a breath of air stirred, but the speed of the vessel sent a breeze whipping over the poop of the steamer where a group of battered men stared fixedly over the long frothing path of the screw. several of the group wore bandages, two, unable to stand, sat in steamer chairs, all had the pale faces of all-night watchers, but every eye in the crowd scanned with feverish intensity the spangled ocean over which they fled.

the wind snatched at the clothes and bandages of the intent men. masses of seaweed swept like gray blurs down the sheer of the tug's wake. just beneath them the propeller rushed with watery thunder.

"yonder she rises!" cried one of the watchers, pointing at two wireless masts that rose like the fins of a racing shark above the green surface of the sargasso.

"yonder she rises!" repeated a voice amidship, and more faintly still came the repetition from the bridge, "yonder she rises—hard a-port!"

a sudden shift of the rudder shook the vulcan from peak to keelson. next moment the tug was speeding squarely across a seaweed field, and another crook was added to the smoke mark in the sky. the vulcan's blunt prow drove through the seaweed at a great rate, while the clammy mass swung back together not sixty yards behind the churning screw.

a strange race had developed between the tug and submarine. when both crafts were on the surface in open water, the submarine had a knot or two advantage of the vulcan and could have picked her up in four or five hours. but early in the night caradoc had discovered that the powerful screw of the steamer, designed, as it was, to propel vast loads, could make the higher speed across the algae beds.

on the other hand, if the submarine dived to escape the drag of the weed, she again became the faster craft. but, in this instance, when the submarine dived, the vulcan would immediately take to the open lanes and do more than preserve her distance. these constant shifts and turns explained the ricocheting course that was marked in smoke across the whitening dawn.

the submarine stood well out of water and skimmed along in the pink gleam like a long, slender missile. its flat deck, wireless masts and conning tower stood etched in black against the morning light. she was consuming a fairish stretch of open water at a high speed.

"she's game for a long chase," observed hogan, gently shifting a wounded arm in its sling.

leonard madden replied without removing his eyes from the rushing boat, "she has to be. all of germany's naval plans depend on her destroying us."

"it does—and, faith, may oi ask why?"

"if we get to antigua and report this to the british admiralty, how long would this sargasso reshipping arrangement last?"

"right you are there, misther madden," agreed hogan at once. "we'd woipe 'em out, wouldn't we? we'll make it, too. if we stood off th' little didapper all night, you know we can all day."

madden considered the fleet little vessel. "no, i rather think she will capture us."

"and how's that?"

"the sargasso doesn't extend indefinitely. in fact we are nearing the southern limit. have you taken a look forward?"

"no, i haven't," said hogan, taking vague alarm at madden's tone. "what's wrong?"

"i don't see many more big seaweed fields ahead. if she gets us in open water——"

"why bad luck to it! bad luck to it, oi say!" cried hogan as the wind whistled about him; "running us out o' the bushes loike a swamp rabbit."

just then the submarine veered off her straight course somewhat to extend her open water run for two or three miles up the edge of the field. a length view showed her to be a delicate looking craft. her sharp prow cut the water with hardly a ripple, in sharp contrast to the vulcan, which shouldered up a waterfall as she lunged forward.

suddenly, and rather unexpectedly, the submarine porpoised. there was a swash of foam, and she was gone.

the men on the poop stepped around to the side of the tug and stared anxiously southward. bits of flotsam mottled the blue expanse, but it really appeared as if the saving drift weed were thinning to nothing. hogan glanced back over the way he had come.

"sure it'll be a fair field and no favor, sweet peggy o'neal!" he hummed nonchalantly under his breath.

at that moment a violent shaking went over the vulcan, and the short boat swung her prow about with tug-like promptness. it was as if the stout little craft had swung around on her heel.

"faith and would ye shake a man's arrum off!" shouted hogan at nobody in particular. "and are ye going back to meet the friendly little wasp?"

that was exactly what caradoc was doing. he had swung the vulcan about in less than a hundred yard circle and was plowing straight back the way they had come.

the crowd on the poop held their breath at the daring maneuver. tug and submarine were now rushing at each other full tilt, only one ran under water, the other on the surface. suppose the submarine should thrust up a periscope for an instant—a cough of the torpedo tube and the vulcan would be blown to scrap iron.

the men on the poop ran forward, staring with frightened eyes over the gray-green soggy field through which the vulcan ripped her way.

it seemed fantastic to think that somewhere under that lifeless weed human beings spun swiftly along, freighted with the most terrific engine of destruction. what strange warfare! who could have fancied that when savages began to use clubs to maul each other it would end in this diabolical refinement! weapons, weapons, weapons—the history of man's undying savagery working under new forms of civilization! the war submarine—what a monstrous offspring of genius!

the sun rose like a white-hot ball in the brazen sky and the men held to the rails, mouths open, and stared ahead into the safe open water, expecting every moment for the vulcan to spatter skyward in a volcano of fire and steel.

the boat itself rattled along with that insensibility of mechanism that sometimes astounds an apprehensive man. twenty minutes later, she turned into the open lane, and was rushing westward again at full steam.

an immense relief spread over the crew. galton, who stood on the bridge at the wheel beside caradoc, blew out a long breath and wiped the sweat from his face, farnol greer began a windy whistling of "winona, sweet indian maid." madden felt as if a weight had been lifted off his brain. hogan was humming a tune. but all eyes turned anxiously seaward, to see where the submarine would "blow."

ten minutes later, a distant ripple in the water caught their watchful eyes and the wireless masts popped up, on the opposite side of the great weed field, four or five miles distant.

a spontaneous cheering broke out on the vulcan's decks.

"double crossed! double crossed!" bellowed hogan.

"back track! we put one over! hurrah for cap'n smith!" they shouted above the pounding of the engines.

everyone but caradoc wore the fixed exultant grin of the man who outwits his rival. the submarine had been thoroughly outgeneraled. north and west of the vulcan lay the whole sargasso for an endless chase. the diving boat had lost the great advantage of having the steamer cornered.

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."