etched against the horizon lay a stumpy masted vessel that seemed as still and dead as ocean that rotted around it. she had not a sail aloft nor a plume of smoke in her funnel. for the moment this lifelessness was not observed by the hungry castaways. a joyous medley arose from the dock.

"th' vulcan! hit's th' vulcan! th' good vulcan! we'll 'ave full rations t'night, 'at will! hurrah!"

they fell to cheering. voices arose in confusion.

"vulcan ahoy! vulcan ah-o-oy!" they bellowed in an effort to span the miles with human ices.

"say, lads, she ain't movin'!" cried someone making the surprising discovery.

"faith and phwat's th' matter with her now?" exclaimed hogan in exasperated wonder.

a silence fell over the boisterous group.

"out o' coal," hazarded galton, "that's w'y she harsn't got back no sooner."

"w'ere's 'er sails, then?"

"a tug couldn't do nothin' with sails—she isn't made for sails!"

"it ain't w'ot ye're made for, hit's w'ot ye can git in this blarsted sea!"

"maybe 'er machin'ry's broke?"

"maybe they're hall sick?"

"or dead?"

"maybe——"

madden hurried to his cabin and returned with binoculars. the men foregathered curiously about him as he scanned the vessel. he ran his eyes over the tub from stem to poop. she stood out with absolute distinctness in the glaring light. he could see her high prow, the swinging buffers along her side, the wide-mouthed ventilators. he could even make out her name in rusty letters under the wheel-house. her small boats were in place, but he saw neither life nor movement aboard. she appeared as deserted as a pile of scrap iron.

"w'ot are they doin'?" queried galton.

"nothing." madden was puzzled over the strange condition of the tug.

"ain't they crowdin' to th' side, sir, lookin' at us and fixin' to come to us?"

"nobody's on her," replied madden. "at least i don't see anyone."

"w'ot! w'ot! nobody on 'er! is she deserted, too? just like the minnie b!" chorused apprehensive voices.

"seems so," frowned madden, then he made up his mind quickly and moved over to the small boat which had been hauled up on the forward pontoon.

"fall to, men, lower that dinghy. we'll go over and see what's the trouble."

the crew went about their task with a sudden slump of enthusiasm.

"if the crew's gone, sir," mumbled one of the men, as he paid out the rope, "w'ot's the use goin' across?"

"to get to the tug, of course."

"an'w'ot'll we do?"

madden looked hard at the cockney. "get the provisions aboard if nothing else."

"there wasn't none on the minnie b, sir."

"what's the minnie b got to do with the vulcan? we're going to run the tug and dock out of this sea, crew or no crew—ease away on that rope, mulcher. let go! now climb down, galton, loose the tackle and swing her in alongside the ladder."

when the cockneys obeyed, madden ordered the whole crew into the small boat. they climbed down the ladder one by one with a reluctance madden did not quite understand at the time.

fifteen minutes later, the little boat, loaded down to her gunwales, set out for the tug. four oarsmen rowed, one man to the oar. the slow clacking of shafts in tholes echoed sharply from the huge walls of the dock as the dinghy drew away through the burning sunshine.

at some half-mile distance, the harsh outlines of the walls and pontoons changed subtly into a great wine-red castle, that lay on a colorful tapestry of seaweed, with a background of blue ocean and bronze sky.

as he drew away, madden had a premonition that the dock was vanishing out of his life and sight, that never again would he live in its great walls. like all crafts in this mysterious sea, it seemed completely forsaken, deserted. with a shake of his shoulders he put the thought from him and turned to face the future in the motionless tug that lay ahead.

half an hour later the dinghy drew alongside the silent vulcan and the crew clambered aboard. as they had suspected, there was no sign of the tug's crew aboard.

although the binoculars had forewarned them of this, the adventurers bunched together on the deck with a qualmish feeling and began talking in low tones, as men converse in the presence of mystery, or death.

"we'll search her first," directed madden, in a tone he tried to make natural.

"yes," agreed greer, "and, men, keep a sharp eye out for lunatics. don't let anything jump on you——"

"lunatics!" gasped mulcher.

"greer and i fancied someone scuttled the minnie b," explained madden with a frown, "but that's no sign such a person is aboard the vulcan."

"they are wonderful like, sir," observed gaskin.

"anyway we'll look her over."

the men agreed and began scattering away, two by two for companionship. presently from the port side hogan raised his voice guardedly.

"oh, misther madden, just stip this way a moment, if you plaze."

the call instantly attracted several other men. they moved across deck. hogan was pointing. "jist th' same as th' other wan," he said gloomily and significantly. "we knew it would be this way, sir. it was th' same hand as done it"

leonard looked with rising dismay at the sinister parallel.

the vulcan also was lying at sea anchor.

in brief, here was conclusive proof that the tug had been abandoned deliberately and with forethought by malone, captain black and the whole vulcan crew. moreover, as in the case of the minnie b, they had deserted their ship without taking a boat or even so much as a life buoy.

the amazed group of men collected about them other members of the searching party, who stuck their heads out of ports and doors now and then to see that no evil magic had set the rigging in flames.

"they all go th' same way," mumbled hogan, staring at the anchor and wetting his dry lips. "oi'm thinkin' it'll be our toime nixt."

"piffle," derided the american half-heartedly.

"it makes no difference what happens," put in caradoc, "we'll see the thing through."

for some reason the men thought better of smith since the fight and his crisp announcement cheered them somewhat.

"she's got plenty o' coal," volunteered galton.

"'er engines look all right," contributed mulcher, "though i know bloomin' little about hengines."

"i weesh i knew what happened to the men," worried deschaillon in his filed-down accent.

"my quistion ixactly, frinchy," nodded hogan emphatically. "misther madden says 'piffle,' but oi say where are they piffled to? did they go over in a storm, or die of fever, or run crazy with heat?"

"they didn't starve," declared mulcher, "for some of th' fellows are in th' cook's galley now eatin'."

madden lifted his hand for attention, "there's no use speculating on what has happened. it's our job to get dock and tug to the nearest port."

"but suppose—suppose——"

"suppose what?"

"suppose th' thing gits arfter us, sir?"

madden stared, "thing—what thing?"

the cockney frowned, looked glumly across deck. galton answered,

"w'y, sir, th' thing that run th' crew hoff the minnie b an' hoff th' vulcan. crews don't 'op hoff in th' hocean for amoosement, sir. some'n' done hit an' that's sure."

"do you mean you object to sailing this tug on account of some imaginary thing?" demanded madden in utter surprise.

"imaginary, sir!" protested mulcher, "if you please, us lads on th' dock, the night th' minnie b sunk, saw something swim off to th' south wrapped hall over in fire, sir. imaginary thing! it bit a 'ole in th' minnie b an' sunk 'er, sir!"

this recalled to leonard's mind the peculiar phenomenon he had witnessed at the sinking of the minnie b.

"what do you think the thing is?" he temporized.

"a—a sea sorpint, sir," stammered a cockney embarrassed.

"sea serpent! sea serpent!" scouted the american. "there is no such thing as a sea serpent!"

"that's w'ot th' hofficers always say," growled mulcher.

"but it is a scientific fact—there's no such thing."

the well-fed gaskin, who formed one of the group, made a bob. "that may well be, sor," he said in solemn deference, "but w'ether there is or isn't such a thing, sor, it's 'orrible to see, either way."

from the banding of the men against him, madden became aware that they had decided on the real cause of the mystery behind his back, and he would have hard work to argue them out of the sea serpent idea.

"you boys saw a shark or porpoise swimming away from that schooner," he began patiently. "i saw it myself. you recall, on that night anything that moved in the water burned like fire. the ship was brilliant, the oars of the dinghy shone. the thing you saw had nothing to do with the schooner."

"then w'ot sunk 'er, sor?"

"aye, an' w'ot come of 'er men, sor?"

"aye, an w'ot come of th' vulcan's crew?"

"could a sea serpent put out a sea anchor?" retorted leonard.

the men stared doggedly at their chief. "we don't know, sor."

"you do know that it is impossible!"

"if there ain't no such thing, sor, 'ow do we know w'ot it can do?" questioned gaskin.

"then do you want to go back and stay on the dock and starve?" cried madden at the end of his patience.

there was a silence at the anger in his tone, then gaskin began very placatingly, "hi'm not wishin' to chafe ye, sor, but th' dock is so big th' lads 'ave decided the sorpint is afraid o' th' dock."

at leonard's impatient gesture he added hastily, "not that hi believe in such things, sor, but hi carn't 'elp but notice that hever'body on th' dock is alive, an' hever'body on th' other two wessels is dead an' gone, sor."

madden turned sharply on his heel. "anybody who knows anything about marine engines, follow me," he snapped. "we must study out a way to start the vulcan's machinery. we're going!"

as he moved down to the doorway amidship that led below, he heard galton mumble: "yes, we'll be going, hi think, down some sea sorpint's scaly throat, but th' tug an' th' dock'll stay 'ere."

if a view of the minnie b's auxiliary engines had put hopeful notions in madden's head of puzzling out their control by mere inspection, a single glance at the huge machinery of the vulcan filled him with despair.

the tug's hull was practically filled with a maze of machinery. her engines arose in a tower of bracings, wheels, gearing, pistons, steam pipes, steam valves, with a multitude of the eccentrics and trip gearings used on quadruple expansion engines.

although he had seen hundreds of steam engines, never before had madden realized their complication until he faced the problem of running this difficult fabric. his proposed task made him realize that the engineer's apprentice, who serves four years amid oil and iron black, learning all the details of these mechanical monsters, is probably just as well educated, just as capable of exact and sustained thought, as the lad who spends four years in college construing dead tongues.

madden could construe dead tongues, or at least could when he left college a few months back, but now his life, the life of his crew, the salving of the dock, and the winning of a possible fortune, depended upon his answering the riddle of this twentieth century sphinx. it was like attempting to understand all mathematics, from addition to celestial mechanics, at a glance.

nevertheless, madden's training as a civil engineer gave him a certain aptitude for his formidable undertaking and he set about it with rat-like patience.

he picked out the main steam pipe, larger than his body, covered with painted white canvas, and followed this till he discovered the throttle, a steel wheel with hand grips with which he could choke the breath out of the monster engines. beside this were control levers. on the steam chest lay a half-smoked cigarette, as if the engineer had been called suddenly away from his post.

madden turned the throttle, pushed the levers back and forth, and listened to clicking sounds high up in the complexity of the engines. he knew that every lever threw long systems of vents and valves in and out of play. a wrong combination would easily wreck all this powerful machinery. he was tackling a delicate job—like juggling a car-load of dynamite.

an oil can sat under the throttle. the amateur engineer picked up this and a handful of greasy tow. engines require constant oiling. madden had never watched an engineer ten minutes but that he went about poking a long crooked-necked oil can into all sorts of hidden inaccessible places.

madden thought if he tried to oil the engine, he might learn something about it. he glanced around for the usual myriad little shining brass oil cups stuck, one on each bearing. to his surprise, he saw none. the machinery of the vulcan was lubricated by a circulatory compression system, which used the same oil over and over. madden did not know this, so it threw him off the track at his first step.

no one had followed the boy into the engine room, so now he was about to go on deck and commandeer a squad, when, to his surprise, galton appeared at the top of the circular stairs, whistling a rather cheerful tune. he leaned over the rail and called down heartily:

"do you want me, mr. madden?"

"yes, come along. i wish you knew something about machinery."

galton laughed buoyantly. "i'm not such a chump at hit, sor," he recommended.

"you know something about it?" inquired madden in surprise.

"a bit, a bit, mr. madden. my brother charley is chief engineer on the rajah in the p & o, sor."

"ever work under him?" asked the american hopefully.

"two years, only two years, sor. never did finish my term an' get my papers. often's the time 'e's begged me to do it, mr. madden. 'e'd say, ''enry, me boy, w'y don't ye finish your term and git a screw o' sixteen pun' per, but i was allus a——"

"that's all right!" cried leonard delightedly. "i don't care whether you're a full-fledged engineer or not. you're hired for this job. understand? you'll get full wages, and then some. i'll——"

"oh! i can 'andle a little hengine like this, sor. that's th' inspirator, sor," he pointed. "that's th' steam chist. in th' other end is th' condensing chamber. that little hegg-shaped thing is——"

"that's all right; i'm no examining board. just so you can run it and keep it running. now i'll get a gang at the furnace, if the boys have got over their sea-serpent scare by this time."

"they're jolly well over that, sor. me and mulcher 'ave decided as 'ow we're goin' to kill that sea sorpint, if it comes a-bitin' into our tug, sor."

madden looked at his willing helper curiously. "kill it—how are you going to kill it?"

"dead, sor, yes, kill it dead, sor." galton nodded solemnly, "my brother charley, cap'n o' th' cambria, sir, in th' 'amburg-american line, 'e learned me to kill sea sorpints, w'en i was jest a l-little bit of a—a piker, sor. an' i n-never forgot 'ow 'e told me to do it. you climb up th' mainmast, sor, w'ere you can git at their 'eads, cross your fingers for luck, an' blow tobacco smoke in their eyes. they 'ate tobacco smoke an——"

leonard stared at the fellow, with a sinking heart. he was drunk. as to whether he knew anything about marine engines or not, there was no way to find out.

the effect of the long strain of heat, hunger and anxiety now told on madden in a wave of unreasonable exasperation.

"you boozy fool!" snapped the officer, "you haven't sense enough to run a go-cart. go down and start a fire in the furnace—can you do that?"

"shertainly," nodded galton gravely, "mr. madden, i can do anything. go bring me th' furnace, and i'll put a fire in it that quick. i'll start it now."

here he stooped unsteadily, picked up a piece of oily tow, and before madden knew what he was about, drew out a match and set fire to the greasy mass.

leonard made a jump, planted a cracking blow between galton's eyes. the fellow went down like a tenpin and lay still. the american stamped out the blazing tow before the fire spread on the oily floor.

just then he heard a yelling from the upper deck. hardly knowing what to expect, he dived for the circular stairway and rushed up three steps at a jump.