"If Mr. Peters went with me, sir, it doesn't seem as if there would be any great danger," Sidney suggested, and after a long pause the keeper announced his decision. "Keep right at work on the boat, Sammy, an' if she's in good condition when the fog lifts, we'll argue the matter a little; but I ain't willin' to agree off hand that it shall be done." The first assistant appeared to be satisfied with this questionable promise. He at once began to explain in detail how he proposed to perform the necessary labor on the motor boat, and where it would be possible to get the needed materials. Sidney listened intently until Mr. Peters had exhausted the subject, and then he asked timidly of the keeper: "Did you say, sir, that you hadn't any fog signal?" "Ay, lad, them was my very words. You've been over pretty much the whole of this 'ere ledge, an' I reckon you didn't see anything that looked like one, eh?" "No, sir; but when I came in here, before seeing the tower, I heard what I thought was a fog signal, and it has been going ever since." "True for you, my lad, but what you heard, an' are hearin' now, is the whistlin' buoy, anchored off here a couple of miles to the east'ard, an' I reckon you're enough of a sailor to know what sich things are." "I've heard them often; but never knew how the noise could be got out of a buoy which had no person to attend it." "When you have the time there's nothin' to hinder your readin' what the Board says about whistlin' buoys; but I won't promise that you'll be any the wiser after doin' it, for in all these years I haven't been able to get it through my head, though I've figgered out a gen'ral idee of how she works. The top of the buoy is shaped a good deal like a pear, an' measures about twelve feet across the widest part. Inside the upper part, an' runnin' down into the sea to a depth of thirty-two feet, is an iron pipe thirty-three inches across it. Right at the very top of the pipe, an' showin' above the whole thing, is a 10-inch locomotive whistle, connected with some little tubes, which the inspector says make a piston-and cylinder movement, whatever that may be. "Of course these 'ere buoys are anchored in deep water, an' it stands to reason that they rise an' fall on the waves, consequently the water inside the big pipe pumps up an' down, compressin' the air till it jest nat'rally has to escape through the whistle, makin' the noise. The whole thing was invented by a man named Courtenay, an' I'm bound to say he must have had a big head on his shoulders to think out sich a contrivance. It may be, lad, that you'll understand it better by readin' from the report; but I can't tackle the big words, an' don't know a piston or an apex from the Queen of Sheba, consequently it don't do me any great amount of good to puzzle over 'em.