Thump, thump, thump.

“Hi, Jack! Hello, Ray! Come, wake up. Think you can sleep all day? It’s half-past five.”

Thus were the two lads aroused next morning by Mr. Warner as he came from his room across the hall.

“Come,” he added, “tumble out. The boat will start for the rock before you are dressed.”

This was enough to stir both lads, for they had set their hearts on taking part in the tussle with the waves to gain the top of Cobra Head. They were on their feet in a jiffy and presently were whisking on their clothes with little regard for sartorial effect. Jack managed to get his undershirt on wrong side out, as boys frequently do when they are in a hurry, and Ray discovered that he was trying to get his left foot into his right shoe. But in a remarkably short time they had adjusted things, dashed cold water in their faces, given their hair a brief but effective brushing, and emerged from their room.

Ray’s arm was a little stiff at first, but the iodine that had been applied the day before had taken most of the soreness out of the cut and he positively refused to keep his hand in a sling any longer.

“I’ll keep on the bandage, but I won’t wear a sling. Makes me feel like an invalid,” he told Jack as they descended the stairs and joined Mr. Warner in front of the lighthouse cottage.

Captain Eli was of course snugly tucked in bed and snoring lustily at that unseemly hour, and since the engineer and his young companions were destined to be early risers during their stay on the island it had been decided that they take their breakfast with the crew in the main mess-hall.

Bongo, the big negro cook of the outfit, was just sounding his call to quarters on the bottom of a big dishpan when the three entered the long low building. There was little of a decorative nature about the arrangement of the tables in the hall. There were two, that extended the full length of the room and were flanked on either side by long backless benches.

In twos and threes and groups of half a dozen the burly lighthouse builders came from the bunk-house to the mess-hall. They were a happy-go-lucky lot who could not resist a little horse play by way of a morning’s greeting and the fisticuffs and good-natured chaffing that resulted made Bongo’s face shine with merriment as he hustled about the room with big bowls of steaming victuals.

Jack, Ray and Mr. Warner crowded in beside the foreman, Big O’Brien, and fell to with as much zest as the rest of the men. The breakfast was of a rather coarse nature, to be sure, consisting chiefly of baked beans, liberal slices of salt pork, thick slices of bread, canned peaches and coffee as strong and black as Bongo could possibly brew it. But Jack ate with a decided relish, nor did he pause to compare the breakfast with those served at Drueryville.

During the entire meal Mr. Warner and Big O’Brien were in earnest conversation, to which Jack and Ray were very attentive. The men were discussing the details of the expedition to the rock, and as the lads listened to the preparations that were being made they realized more and more that they were about to embark upon a hazardous undertaking.

By quarter of six the foreman and the engineer had drained their cups and pushed back their plates. Others of the crew were doing the same thing when O’Brien stood up and shouted, “Come, bhoys, ye have t’ sha-ake a leg. In haf en hour-r we’ll man t’ bhoat and r-run out on t’ last o’ the down tide. That’ll give us an hour-r t’ fuss ar-round befer it sthar-rts a-racin’ in agin. Come on, Mike, and you, Sandy, and Lafe there, git a wiggle on yez, yer all part of the boat crew.” And presently there was the scuffle of many feet and the rasp of the benches being pushed back, and five minutes after O’Brien left the mess-hall Bongo had the place to himself.

Before collecting his crew the foreman singled out three sun-tanned workmen who were among the last to leave the mess-hall and with them at his heels the big Irishman went into one of the tool sheds. Shortly all four reappeared, one dragging a little brass cannon, such as is used by coast guards, while the others carried a big open box, into which hundreds of feet of sail cord was coiled upon pegs.

The cannon was hauled to the cliff’s edge, loaded and sighted by one of the weather-beaten trio, so as to hurl a rocket-like projectile over the ugly gray rock out there where the breakers curled.

Of course Jack and Ray could not entirely understand what it was all about, but, while they were wondering, Mr. Warner, who had gone to his office for his steel surveying tape and plumb line, arrived on the scene and explained that, when the men succeeded in landing on Cobra Head, the projectile would be fired so as to carry a rope to them. And when they had all things fast, a breeches-buoy would be rigged to carry more men from the cliff to the rock.

Upon Mr. Warner’s return, O’Brien quickly gathered his crew and, with Jack and Ray among them, they started down the pathway that led to the beach where the two whaleboats were moored. Into these the men swarmed and a few minutes later the craft shot away from the strip of sand and headed north inside the reef and toward the dangerous Cobra Head.

It was low water and the long jagged reef, exposed from end to end, looked exactly like a giant of the species after which it had been named. Outside, beyond the wicked rocks, rolled the Atlantic; great ground swells heaving in restlessly and thundering against the granite barrier with a grumbling roar. Jack and Ray, who sat in the stern of the whaleboat with Mr. Warner and Big O’Brien, were fascinated by the sight.

But, although the waves piled up outside, the strip of water between the island and the beach was unruffled, so far as the surface was concerned. Under this calm exterior, however, were currents and cross-currents that slipped oilily over the granite-strewn bottom in spite of the fact that it was the hour for slack water. Jack could see from the way Big O’Brien handled the tiller and the strength that the men put in their tugs at the oars that the force of these currents was tremendous, and he wondered what that strip of water would be like when the tide turned and began to come in.

As the whaleboat proceeded northward and approached the big rock the currents became more vicious. They ripped and swirled and licked at the side of the sturdy vessel like the advance guard of Neptune’s forces defending the rock from the invaders. The men were bending to the oars now and grunting with each stroke, and Jack and Ray could see the muscles in their knotted arms stand out under the strain. Slowly but surely the boat drew nearer the tremendous boulder, and as the lads got a closer view of the pedestal on which the new lighthouse was to be erected they realized why Mr. Warner had cause to worry about the outcome of the expedition.

For fifty feet about the great chunk of granite the water fairly boiled with eddies and currents and the force of the heaving swells of the Atlantic. Here all these met and struggled for supremacy, and the ugly sides of Cobra Head were lashed and pounded by tons of water hurled against them. It seemed folly for a craft even as stanch as the big whaleboat to venture into that turmoil and dare the approach of the rock.

And to make the situation harder the head presented a grim and foreboding surface to the adventurers. Indeed, there did not appear to be a crack, or crevice into which the men could get a foothold when they attempted a landing, and if there really were any they were well covered with slippery brown rock weed and kelp that draped the sides of the massive stone. In truth, as Jack gazed upon the grim barrier, it looked to him like the great shaggy head of Medusa with her snaky locks tossed about in the hissing breakers. And the thunder of the tumbling water was almost deafening.

“Mighty ugly looking, isn’t it?” shouted Mr. Warner, for a shout was necessary to make his voice heard above the roar.

“I should say so,” cried the boys, trying to suppress their excitement.

Big O’Brien cupped one hand about his mouth and shouted to the boat crew:

“Row on, boys. Pull, an’ we’ll go ar-round t’ blitherin’ thing t’ see if ther-re be a place fer a fly t’ sthick on.” And the men bent to once more and urged the craft forward, keeping outside of the ring of troubled water as much as possible.

Slowly they made their way round the circle, the whaleboat pitching and rolling like a cork. Foot by foot they moved through the boiling, foam-flecked water and all the time Big O’Brien and Mr. Warner scanned the great granite crag for a place to attempt a landing.

And at last they found it. To be sure it was not much of a landing place, but then it was better than a sheer wall of granite covered with slippery kelp. On the ocean side where the great breakers dashed in with a roar the rock weed had been all torn away by the force of the water. Ages of erosion had worn soft spots in the granite away, too, until there remained a slopping trough into which the water dashed with a hiss and fountained twenty feet in the air.

The constant action on the sloping side had worn the hard stone as smooth as glass and the dashing of the wave plumes had pitted the rock here and there above, so that a man of great agility could hope to gain the top if he moved fast enough and could beat these curling tongues of water that shot against the rock and licked it clean.

“Tiz there ’er no place, Chief,” shouted the foreman to Mr. Warner. Then, as the engineer studied the situation, he shouted again. “May we be per-rtechted whin we tr-ry too; fer if wan o’ thim waves hits yez a slap in t’ back ’twill be Davy Jones’ Locker t’ next stop. They’ll suck yez under in a whink, an’ yez’ll niver see daylight agin. No shwimmin’ yez ivver learnt will save yez agin the undertow.”

“Well, the engineer who made the survey last year did it, O’Brien, and I guess we can do as much,” called Mr. Warner.

“Sure-re yez ’er a Kilkenny cat fer pluck,” said the foreman, “but I’m wid yez. Hi, bhoys, we’ll make a landin’. Tiz me an’ Mr. Warner what does it an’ don’t anither wan o’ yez even think o’ thr-ryin’. Yez hear-r me now. I’ll lick t’ life out o’ eny man who even sthands up in t’ bhoat. Here, Lanky Sims, yez ’er t’ bist sailor in t’ outfit; take t’ tiller and mind yez kape her hull. Jist a shlip an’ she’ll be smashed t’ kindlin’ agin t’ r-rock an’ we’ll all be at t’ bhottom.”

Lanky Sims, a tall, raw-boned Yankee who had been brought up on the high seas, came from the bow and took O’Brien’s place. Mr. Warner turned solemnly and shook hands with Jack and Ray, and O’Brien did the same. Not a word did they utter, but the lads understood, and a lump as big as an apple came into Jack’s throat.

The engineer and the foreman made their way to the bow of the boat. Then Lanky Sims took a fresh quid from a black plug of tobacco, spat over the side and shouted:

“Yo-heave-ho, boys!”

And the men bent to the oars with a will. Sims took the craft out toward the open ocean, then turned her, and with the swells at her stern started to ride in slowly, keeping his eyes pinned on the sloping trough of rock into which each big wave plunged and surged aloft with a gurgling hiss. Nearer and nearer they drew, the men rowing with short strokes and keeping their great bodies alert and ready to obey Sims’ orders. Mr. Warner had decided to try first, in spite of the Irishman’s protests, and he stood waiting in the bow, one foot on the gunwale and his hand resting on Big O’Brien’s shoulder to steady himself.

Sims watched the waves with calculating eyes. Not a muscle in his face moved. Not a nerve in his body quivered. Closer and closer to certain destruction moved the pitching boat. A great wave raised it, held it trembling aloft for a moment, then slipped out from under it and shot into the trough, spurting foam and water aloft and drenching the entire crew. And the moment its force had been spent and the water began to suck backward Sims gave the expected order.

“Yo-heave-ho!” he roared and bent his body forward. The oars dug deep and the whaleboat shot forward! Mr. Warner hesitated a moment, then jumped! Into the trough he dropped and up the slippery granite he scrambled. He reached the first niche, the second, the third. He was ten feet up, twelve, and now fifteen. Then Sims shouted:

“Back, boys, back water quick. Here comes another.”

The oak oars bent and creaked under the strain. The whaleboat shot backward and full into the oncoming wave. For a fraction of a second it stopped dead and every timber quivered. Then with a rush it shot backward again and the wave slipped under it and hurled itself into the trough, its great curling tongue licking up the side of the rock as if seeking to tear Mr. Warner from the little niches to which he clung.

But the engineer was safe. He was drenched with foam and spray, but he was well out of the way of the dangerous water. Up he climbed, slower now, feeling his way from place to place; while the boat backed off to a safe distance and the crew watched his progress. Finally he gained the top and stood erect. Then, what a shout went up from the men in the whaler!

It was O’Brien’s turn now. The big Irishman stood up in the bow while Sims began maneuvering the boat once more. Again it approached the rock slowly, riding in on the long waves until it began to get dangerously near the big boulder. Then the tall Yankee at the tiller waited, tense and alert, watching his chance to run in immediately after a big wave had spent itself, and back the boat out of danger before the next wave could hurl it against the granite and shatter it into splinters.

The chance came. A big wave burst with a roar against the rock, the spray splashing in all directions. Then, as the tons of water slipped back again, Sims roared his “Yo-heave-ho” command.

In shot the boat against the curling, sucking eddies. Big O’Brien balanced a moment on the gunwale and leapt forward. Into the trough he dropped. Then began the scramble for the first niche before the next wave surged in and seized him. Up he climbed over the slippery stone. He reached the first of the grooves and was trying to get a foothold in another when—his hand slipped! The next moment he shot down the trough and back to the very spot upon which he had landed! Frantically he struggled to his knees, then to his feet, only to slip prone again. Then with a hiss and a roar the next wave came curling in. He was doomed!

The force of the water hurled him up the slippery trough, raised him high in the air and dropped him backward, helpless, into the spume at the base of the rock.

“Merciful Providence protect him! He’s gone!” cried Sims, turning white.

Jack and Ray were numb with horror. Big O’Brien had been whisked from the face of the earth like a straw.

But before they could collect their scattered wits Lanky Sims’ voice was heard again above the roar of the water.

“Look! Quick! There he is! On the port side! You boy, grab him! There! See him!”

Ray saw a distorted mass of clothing and legs rise to the surface just under him. It was whirled round and round by the force of the undercurrent for a brief instant before it started to sink again. Blindly the lad reached over the side and clutched. His fingers closed upon a cold and clammy wrist, to which he clung despite the surging and tearing of the current.

Forgetful of the danger for the moment, Lanky Sims let go the tiller and reaching a long arm into the water seized hold of the big foreman too. Then together they dragged him over the gunwale and into the boat. And while Jack and Ray took care of the all but drowned foreman, Sims directed the whaleboat out of the lashing water and toward the open sea where there were only the long rollers to combat.

The two boys worked manfully over Big O’Brien. First they got all of the water out of his lungs. Then with him lying prone in the bottom of the boat they started artificial respiration, as Jack had been taught it by the football coach at Drueryville Academy. For fully fifteen minutes the boys labored over the foreman while Sims and the rest of the crew looked on in silence. And gradually their efforts told, for O’Brien’s eyelids quivered once or twice and finally opened. Two red spots began to show in his ashen cheeks, and after a few moments he regained consciousness.

“Phwat happened?—ugh—O, shur-re I know. The big wave caught me, huh?” he said rather thickly as he sat up.

“It didn’t on’y ketch ye but it smashed t’ life ha’af outen ye,” said Lanky Sims.

“How about Mr. War-rner,” demanded O’Brien, turning and looking toward the big rock. Then for the first time the men in the boat thought of the engineer.

There on the top of Cobra Head stood the lighthouse builder. He had seen the accident and the rescue as well, and Jack could guess what his feeling must have been as he waited there for a signal to tell him whether his foreman was alive or dead.

“Wave to him, O’Brien. Wave your hand and show him that you are still alive,” cried Jack. And the big Irishman struggled to his feet and, holding on to Lanky Sims, waved and shouted as loud as he could.

Mr. Warner answered the signal with a warning wave, which told the men in the boat quite plainly that he wanted them to keep off and not attempt to land another man.

“Sur-r I’d like t’ thr-ry anither fling at it jist t’ show meself that I can’t be bate be a duckin’, but if the boss sez ‘No,’ thin ‘No’ ’tiz. Come on, Lank, thur-rn t’ boat and we’ll go back t’ th’ island.”

During the return journey Jack and Ray kept their eye on Mr. Warner. They saw him scrambling about on the rock, making measurements and marking off various sections of the rugged Head. Then they saw him send a signal to the men on the cliff who waited to fire a lifeline to him. They saw, too, the puff of smoke from the little brass cannon and they watched the rocket with the line trailing out behind it describe a big arc over the rock and fall into the sea beyond, dropping the rope almost into Mr. Warner’s hands.

The engineer began to haul in immediately and presently he dragged out of the surf a heavier section of rope to which the line was fastened. This was the cable upon which the breeches-buoy was to be suspended, and Mr. Warner spent some time in making the end secure over the top of the big lump of granite that formed the cobra’s head. The men on shore worked quickly at rigging the buoy, too, and by the time the boat crew had landed and made its way up the promontory, stone cutters were already being sent down to the rock to level its surface and build the tower that was to support the aerial cableway. And, when Jack saw this, he realized that Cobra Reef had been conquered and that the lighthouse was actually under way.