As soon as the trio began their tour of inspection of the construction camp Jack’s curiosity about the big blocks of granite that looked like sections of a jig-saw puzzle was revived, and the first question he asked of Mr. Warner was:

“What were you going to tell me about that granite?”

“Oh, yes,” said the engineer; “I haven’t said much about lighthouse building yet, have I? Well, we’ll begin at the proper place, which is the beginning, and I’ll outline to you and Ray just what we hope to do here on Cobra Reef. I don’t know whether you two have studied that big boulder out there that looks like a snake’s head, but if you have you’ve noticed that it is about fifty feet across in either direction and that at low tide it stands eighteen or twenty feet out of water. Under those circumstances it is not going to be as difficult to build a lighthouse there as it would were the rock submerged all day. As a matter of fact, it is never totally under water, although sometimes the seas break completely over it at high tide.

“Last year when it was decided to supersede the Hood Island light with a more modern structure (you’ve noticed that the present tower is quite antiquated in appearance) engineers from the Bureau of Lighthouses came here and after a great deal of trouble landed on Cobra Head and ran a survey across the rock. Their figures were taken to Washington and studied, and the kind of a lighthouse necessary to crown the reef was decided upon.

“The decision resulted in the adoption of the most common form of light which is known as a monolithic structure; a single shaft of stone. Lighthouses of this character are usually built of granite prepared as the granite you see over there on the cliff’s edge. There are other good lighthouse materials, however. Some structures are built of reenforced concrete, some of steel, and some are nothing more or less than wooden buildings built on steel supports.

“But granite is considered superior material where the light is wave swept, as this one will be. In building a lighthouse of granite it is very necessary that when the pile is completed it shall be almost as solid as a single section of rock. To make this possible a European engineer, a long time ago, devised the plan of making each block of stone lock into the other by means of dove-tailing them. This is accomplished by having the stonecutters in the quarry yards chip projections on the top and one side, and indentations on the bottom and remaining side of the granite building blocks, so that when the stone is put in place the two projections fit into two indentions on the side of the block next to it and the top of the one it rests upon, and the indentions on the side and top are ready to receive the projections of the next stone.”

Here Mr. Warner tore a sheet from his engineering note-book and sitting on the edge of one of the big blocks he sketched out a cross section of the foundation of the proposed lighthouse as well as a sectional view of the structure itself, thus giving the boys a clear idea of how the work would be done.

“The work of shaping the stones is all done at the quarries; indeed the entire lighthouse is erected stone for stone in the quarry yard so that every piece fits perfectly. The blocks are then numbered and the structure is taken apart and shipped here. If you’ll notice each of those granite blocks is numbered according to position and section. In that way there is no delay in preparing materials while construction work is under way.”

“My, but that’s interesting,” said Jack. “I did notice that each block was marked, but I had no idea that building a stone lighthouse could be made as simple as all that.”

“Oh, it may sound simple,” said Mr. Warner, “but you just wait until we begin operations. Then it won’t seem so easy.”

“What gets me,” said Ray, “is how you are going to get all of those big chunks of stone over to the rock. Why, some of ’em look as if they weighed five or six tons. Also, how on earth did you get them up on top of this cliff?”

“I’ll answer both of those questions at once,” said Mr. Warner. “You are quite right, Ray; the blocks do weigh a great deal. In fact, some of the larger ones to be used in the base of the lighthouse weigh fully four tons. Under those circumstances it must look like a tremendous task to get them up to the top of the cliff and later take them over to the rock. You see, if Cobra Head had been larger and the water in the vicinity less treacherous, the lighters that brought the stone here from Portland would have landed it on the rock. Under the existing conditions, however, this could not be done and the next best thing was to land the material on Hood Island. To leave it at the beach, where we came ashore, would have been out of the question, for it would be necessary later on to reload it on lighters, section by section, and take it to the rock. Finally we decided that we would adopt the same methods as those used by the English engineers in building several famous lights; that is, we planned an aerial cableway between the top of the cliff and Cobra Head rock, thus providing a short and safe means of conveying men, supplies and materials to the reef’s head. That steel tower yonder, which the men are re-rigging, and that donkey engine on the cliff’s edge, were installed a month or so ago, and every time a lighter with stone and supplies of a cumbersome nature came in, a temporary cableway was rigged from the tower to the mast on board the boat and the supplies brought ashore in that way.

“Our trip to the rock to-morrow will be to carry a line out there with which to rig up a temporary breeches-buoy outfit such as coastguards use in case of a wreck. In this men will be sent to the reef to drill holes and make an anchorage for the aerial cableway which will be built immediately. Then everything will be ready for the real construction work.”

Mr. Warner paused again and sketched a map of the reef and the island showing how the cableway would be built between the island and the head of the reef.

“What sort of a foundation will you have for the light, Mr. Warner?” asked Ray.

“Oh, I was coming to that. Here’s how we will proceed with the work. To-morrow we will land on the rock, providing Neptune is willing. Then while some men are drilling holes in which to put the ringbolts to hold the reef end of the cableway, other men will start chipping away the humps and bumps on Cobra Head. That lump that looks like a head itself will have to be cut away and the top of the hood will be made as flat as possible. It will not be necessary to dig very deep into the rock because the constant erosion of the sea for centuries past has eaten away all the soft parts of the rock, if there ever were any, and all that you see above water now is as firm and as hard as flint. As I said before, we’ll pare it down somewhat in spots and we may be forced to use a little dynamite in the work, though I’ll avoid that if possible for explosives may shatter the entire boulder if they are not used carefully. Then where would we be?”

“I think if that should happen you would have a mighty hard job on your hands,” said Jack.

“You’re right, we would,” assured Mr. Warner. Then he continued, “When the chipping is all done and the cableway is in working order, things will proceed as smoothly as the elements will allow. The first blocks will be sent down and put in place. They will be imbedded in cement which will take hold of both the rock and the building block. After the cement is set a hole will be drilled through the granite block and deep into the boulder. A heavy steel bolt will be sunk through this hole and anchored to the reef with hydraulic cement which will be forced home under pressure. When this cement has set the first tier of stones will be as solid as man can make it.

“When the cableway is working we’ll start to build a miniature construction camp out there on the rock. There will be derricks, for one thing, for no man, or group of men, could handle one of those tremendous blocks without some mechanical assistance. It is probable that half a dozen derricks will be built during the course of construction work, for storms will sweep them away in a jiffy once the waves get piling up on the Head. We’ll be lucky if we don’t lose some of our workmen too. There’s many a lighthouse along the coast the building of which has cost more than one human life. This sort of work, my boys, is not the easiest in the—”

“Ow-w-w-w-ye-e-e-e-o! Ow-w-w-w-ye-e-e-o!”

“Good gracious, what’s that,” exclaimed Jack, jumping as if he had been shot.

Ray smiled and turned around slowly. “That’s a conch. Some one’s calling.”

“Yes, that’s Eli Whittaker’s dinner horn,” said Mr. Warner, smiling at Jack’s surprise.

“Call to dinner, is it?” said Jack, smiling too; “sounded to me as if a whole drove of elephants was charging down upon us. Well, if it means something to eat I’ll welcome it as terrible as it sounds,” said the lad from Vermont.

“So’ll I,” assured Ray, “though I don’t know how I’m going to handle a knife and fork with my arm out of commission.”

“Pooh, don’t mind that as long as your mouth isn’t in a sling,” said Jack. “I’ll cut up your food and you can use the fork with your good paw, can’t you?”

“Just watch me,” said Ray.

The sound of the conch was evidently the camp’s signal for dinner too, for as Jack and Ray and Mr. Warner walked back toward the lighthouse they passed scores of men on their way to the long, half-finished mess-hall where Bongo, the dusky cook, was piling a board table full of good wholesome victuals. The men of the crew were of all nationalities, but they were men every one of them. Jack noted the fact that every eye was clear and each moved with a stride that bespoke strength and agility. They were big chested and brawny and Jack did not know when or where he had ever seen finer specimens of manhood, a fact which he remarked to Ray and Mr. Warner.

Four seated about the tiny dining-room of Eli Whittaker’s spick-and-span cottage made the place seem crowded indeed. Eli was his own cook and housekeeper and he was a past-master at both, according to Jack’s way of thinking. That he was an excellent housekeeper was evident from a glance about the neat cottage and the neater light tower. And as for his cooking ability, well, great dishes full of steamed clams, three fat lobsters split in half, and generous portions of corned beef, boiled potatoes and canned corn, all provided eloquent testimony to this fact. The quartet fell to with a will, and Ray, despite his handicap, managed to consume as much as the rest.

After dinner the two lads helped Captain Eli wash dishes, though Ray was of little assistance because of his injured arm. And while they were thus occupied Mr. Warner came in from the camp with word that O’Brien had assured him that all work on the buildings would be completed by evening, and that the next morning everything would be ready for their first attempt to land on Cobra Head.

A little later the engineer took Jack and Ray over to a two-roomed shanty in which he intended to make his office and drafting-room. Here they were shown to the rear apartment where there were several high desks and a number of books. This portion of the building, Mr. Warner informed them, was to be their domain, Jack being given one desk and Ray another.

For half an hour Mr. Warner explained in detail the clerical work that the boys would have to attend to, and before he left he assured them that their daily routine would not keep them occupied more than a few hours each morning and that the rest of the time they would be at liberty to spend with the engineers, or the crew, or do whatever else they saw fit to occupy their time.

Their first duties, however, were enough to keep the lads occupied for some time and Eli Whittaker’s conch was sounding its evening warning almost before they realized it.

“Jiminy,” said Jack, looking up from his books, “it’s time to eat again. I’m hungrier than a bear too. My, what an appetite I’ve developed since I left Vermont.”

“I get sort of hungry myself now that I don’t have to worry about Uncle Vance and his disagreeable temper. If I only had the lifeboat model he tossed overboard I’d be as happy as any one could be. I’m going to get at a new model as soon as my arm gets better, by jiminy, and you can bet no one’s going to get a chance to heave it overboard again. The thing that is worrying me though is whether I’ll be able to remember just how I had the first one built,” said Ray, slipping down from his high stool and joining Jack.

“Tut, tut,” said Jack, “don’t worry about it now. Let’s go and get something to eat.”

When the two lads came out of the office door they noticed immediately that although it still lacked an hour or more of dusk Eli Whittaker had already lighted the lamp in the tower. Jack and Ray watched it shoot forth its single ray of white light periodically as the big lens revolved.

“I’m going up in the tower after supper and learn something about lighthouse lamps, that is if Captain Whittaker will let me,” said Jack, as they walked up the path to the top of the promontory.

“I’d like to have a peek inside of the lamp too,” said Ray. “Let’s ask Captain Eli if he won’t tell us something about the lighthouse service too.”

“Good idea,” said Jack as they entered the cottage.

The boys were not long in bringing up the subject of conversation, for almost as soon as the four of them were seated about the table once more Jack turned to the light keeper and spoke.

“Captain,” said he, “Ray and I are mighty interested in the lighthouse service and we’d like to know a lot about it. Also we’d like to know something about the way the lighthouses are lighted too.”

“Well, as fer t’ way lights is lit I can take you up in the tower later and ye can have a look at my light and I calc’ late I kin tell ye all ab’ut haow ’tis run. But that hain’t ha’af what’s t’ be told about lights. Mr. Warner here knows more about lights than I do an’ like es not he kin reel off them there jawbrakers like ‘equiangular prisms,’ ‘dioptics,’ ‘hyperradients,’ an’ what-not ’thout even stoppin’ t’ think on ’em. As fer me I cain’t never master ’em an’ ’tain’t no use o’ my tryin’. Time an’ agin I’ve clawed through big books on lights an’ such like, but I allus finished ’m ignoranter than when I begun ’un.”

“Pshaw,” said Jack, “we don’t want any of those big words either. What we want is plain English about how lights are regulated.”

“Wall,” said Captain Eli, “I calc’late Mr. Warner could give ye that a big sight better’n I could too, but es fer t’ service; wall, I’ll have a little t’ say on that if ye want t’ hear it.”

“Go ahead, Captain; we’re all ears,” said Mr. Warner. “I’d like to get a good straight-from-the-shoulder opinion from one on the inside.”

“Good,” said the keeper as he began to pour another cup of tea for himself.

“T’ begin with, I kin say that the Lighthouse Service is the finest an’ best regolated department of the United States Government from my p’int o’ view. An’ it has the finest lot of healthy, big-minded, faithful men in it that kin be scraped t’gether on t’ face o’ this earth. I guess it is because these men are in it that the service has been kept as sweet an’ clean as ’tis. You hain’t never heard o’ no political scandals or what-not in this here department, have ye? No, siree, an’ they hain’t agoin’ t’ be none, not while fellers like they got in it stick.

“T’ pay hain’t big an’ t’ hours is long and tedious, but there hain’t a man of us that ’ud shirk his duty in any respect. Just you look over my file of the Lighthouse Service Bulletin which is printed every month. There hain’t an issue what goes by ’thout it has some mention o’ some one doin’ a brave act. Tain’t much of a mention t’ be sure, but we hain’t hankering fer medals er praise. It’s aour business t’ pertect property on t’ high seas an’ save lives when we can.

“Why, there’s some keepers as is so faithful they won’t even take a day off. I read as haow a lighthouse keeper over on t’ other coast in t’ C’lumby River section has only taken two days off duty in twenty-three years. An’ there was the old man who kept the Van Weis Point light down York way. Died when he was ninety-three years old an’ he had been in t’ service fifty-two years. Peers t’ me like a man jest natchelly gits faithful t’ minute he’s set t’ watching out fer some one else’s safety. There’s wimmen in t’ service too, an’ they’re jest t’ same; all Grace Darlings when it comes t’ a p’int o’ nerve. Look at that air woman out Frisco way who stood all night on the platform outside t’ light in a thick fog strikin’ the bell with a tack hammer because the machinery had got out o’ order. An’ there was Ida Lewis, who lived at the Lime Rock Lighthouse near Newport fer fifty-seven years. She was keeper fer thirty-two years after her father died. ’Tis said she saved as many as thirteen people from drownin’ during her life. Hain’t that a record fer ye?”

“You bet it is,” said Ray and Jack, carried away with the old man’s enthusiasm.

“Wall, from that ye can gather what I think o’ t’ Lighthouse Service. No, siree, I hain’t got many kicks agin it. There’s on’y one er two things need regulatin’! There hain’t no pension fer men who git too old fer the service an’ fer men who are injured in the service, but we’re all hopin’ that’ll be changed some day an’ I guess ’twill. An’ in the meantime every one o’ us is workin’ our hardest t’ keep t’ service jest es clean es it can be.”

The two lads were thoroughly impressed by the captain’s recital, and although they did not express it each was of the opinion that if all the men in the Lighthouse Service were as sincere as he, the organization could not help but be free from any taint.

“By George,” said Mr. Warner at the conclusion of the captain’s remarks, “you surely are enthusiastic, but I think you have every reason to be so, for there isn’t a finer lot of men in the world than the five thousand odd who have to do with lighting Uncle Sam’s coast lines. And now, Captain, if you have a couple of amber goggles, which I believe the department is furnishing you men with who have charge of flashing lights, I’ll take the boys aloft and tell them something about the lamp. That will give you time to clean up around before you get ready to go on watch.”

Captain Eli filled his pipe first, then rummaging around in his bedroom produced two sets of goggles which he gave to the boys.

“My goggles are hanging on a peg in the lower light room,” he said to Mr. Warner.

The engineer led the way through the enclosed passage that connected the cottage with the light and presently the boys found themselves in the base of the tower from where a spiral staircase wound its way aloft.

“This is a mighty old light. I think it was built nearly a century ago before lighthouse construction was done as scientifically as it is to-day,” said the engineer. “But, nevertheless, it must have been built well to withstand the elements so long. Although the promontory on which it stands is nearly one hundred feet high and the tower thirty feet tall, Captain Eli has sent in a report on several occasions of waves having broken panels in the lantern, so you can see the old place has stood through some storms.”

The trio were climbing the circular stairs now and Jack noticed, as they wended their way round and round the building, that a long steel wire dangled down into the well of the stairway from the very top of the tower. On the end of the wire was a heavy weight. Of course the boys sought a reason for this, and when they reached the lower light room where Mr. Warner found his goggles, Jack asked him about it.

“That weight,” said the engineer as he adjusted the amber glasses, “operates the clock works in the lamp, which in turn drive the lenses round and round the lamp and produce the flash. Come aloft now and I’ll explain it all in detail, only first put on your glasses because your eyes will not stand the strain of looking into the light.”

The boys did as requested and a moment later they climbed up the last section of the spiral stairs and entered the light. This was a platform on the very top of the tower enclosed by eight panels of glass. There in the center, revolving slowly round and round an incandescent oil vapor lamp was the big lens. Mr. Warner began to explain immediately.

“To begin with, the first forms of light were, of course, wood and coal fires which were burned in braziers. These lights were used in England and in the Mediterranean for a long time. The next step was naturally the candle, but no matter how big they made their tallows, or how many of them they crowded into a lantern, the result was a very weak light. Then came the oil lamps of all varieties. Some burned one kind of oil, some another; a few had one kind of a wick, a few had another type, and so on. Indeed, the experimenting with marine lights has extended over a long period and even to-day there is no universal form of lighting for lighthouses. But that, of course, is because conditions are not the same at each light. Acetylene gas is used for light buoys and similar purposes, and electricity is used where a supply is available, or where it can be manufactured conveniently; but the most satisfactory illuminant, all things considered, is kerosene oil. Indeed, the Lighthouse Service consumes more than half a million gallons of kerosene annually.

“For a long time lamps with from one to five concentric wicks were used in the majority of lighthouses, but these are gradually giving way to incandescent oil lamps, such as the one you see behind the lens there. It is a small compact affair and it gives a most brilliant light and at the same time consumes very little oil. The kerosene, which is supplied from a tank in the lower light room, is heated and vaporized, the vapor mixing with air under an incandescent mantle and burning as steadily as an incandescent lamp in a city street, only brighter.”

“That’s very interesting,” said Ray, who had been watching the lamp for some time. “Now tell us something about the lens, won’t you? How did they come to invent such a complicated-looking affair?”

“Yes, I’ll tell you about the lens. Old-time lighthouse engineers were always experimenting on how to improve the efficiency of a light and when they got through changing the forms of fuel they tried the use of reflectors of various types. Their efforts were more or less successful, but when a French physician by the name of Fresnel came forward with an elaborate system of lenses the science of coast lighting was revolutionized. This lens you see before you is the present-day result of his efforts. It embodies his idea worked out to perfection. You will notice that there is a central lens, or bull’s-eye, and that around it are grouped prisms of highly polished glass. The idea is this: The light throws rays on every side, back, front, top, bottom, and all over. Well, these prisms of glass grasp, as it were, each ray that shoots out at the side and top and literally bend it and shoot it forward. In that way all the light from the lamp is gathered into one bundle and sent out in a given direction, instead of radiating off on all sides. The lens works exactly like a megaphone which your football rooters use at Drueryville, Jack. Do you get the idea?”

“Indeed I do and it is mighty interesting,” assured the young Vermonter.

“Good, and now if you’ve seen all you want up here we’ll go down in the lower light room, for it is hot in the lantern here and besides even with these goggles the bright light hurts my eyes.”

“Mine too,” said Ray, leading the way through the tiny trap door and down the stairway to the lower light room.

“Why do they have some lights flashing and some just a steady glare?” asked Jack when they reached the next room.

“Well, lighthouses to-day can be made to serve a double purpose. They warn mariners of a dangerous coast and by means of flashes they tell vessels which particular light they are near so the seamen know their exact position when they are traveling the coast. This light shows steadily for one minute and then gives a five-second flash. The next light down the coast may give two or three flashes a minute and so on.”

“Do sea captains have to know the flashes of every light along the coast?” queried Jack.

“Indeed they do and a lot more too,” said Mr. Warner.

“What is the candle-power of lighthouse lamps?” asked Ray.

“They vary a great deal,” said Mr. Warner; “this is very small compared with some of our lights. The one on the Highlands, marking the approach to New York Harbor, is said to be of 25,000,000 candle-power. Not long ago we sent one to the Hawaiian Island that had a lens nearly nine feet tall and weighed four tons. It is mounded, or floated rather, on a bed of mercury and makes a complete revolution every twenty seconds, sending out a double flash of 240,000 candle-power. If it were not for the curve of the earth it could be seen more than forty miles.”

“Jiminy, what a light!” exclaimed Jack. “Did you hear that, Captain Eli?” The keeper was just coming up the spiral stairs to go on watch when Mr. Warner completed his statement.

“Yes, that sort o’ makes my little pet up aloft there seem like a taller candle, don’t it?”

“Well, Captain,” said Mr. Warner, “how’s the weather for a clear day to-morrow?”

“Right’s a fiddle, sir,” said the old man.

“And what time is high tide?”

“Tide turns at seven to-morrow—it’ll be full at two o’clock,” said the lightkeeper.

“Good, we’ve got to make a landing on the reef, you know, and we want clear weather for such a venture. I only hope we all come out of it alive,” said Mr. Warner, showing great concern. Then turning to the boys he said: “Well, lads, if you are going to be up to tussle with the waves to-morrow, you’d do well to go to bed. You’ll probably have to bunk together. Which room is theirs, Captain?”

“The little room in t’ so’est corner,” said the captain, adjusting his goggles preparatory to a visit to the light. Then before he climbed the stairs he paused a moment and spoke. “Say, have either of you a watch that keeps good time? I dropped mine this mornin’ an’ now she won’t tick any more. An’ ye know I feel sort o’ lonesome up aloft here when I hain’t got a timepiece about me. Sometimes my watch’s face is t’ on’y friendly face I see fer months, ’ception that o’ old Mitch, t’ lobsterman who lives down t’other end o’ t’ island. He’s the only one on this forsaken strip o’ land except me.”

“Here, Captain, take my watch,” said Jack, hastily handing over the gold timepiece that his father had given him several years before.

“Thank ’e, when ye want it jest let me know. I calc-late I’ll be able t’ fix mine in a day er so.”

Then as he started up the spiral stairs he said:

“Well, good night, boys. I’ll be abed when ye start out fer t’ rock to-morrow, so here’s luck an’ hopin’ ye’ll come back safe. Good night.”

And Ray and Jack started downstairs, both wondering what the next day would bring forth.