“In a tank at the bow,” Nelson answered. “Here’s the supply pipe here.” “And what’s that thing?” “Vaporizer. The gasoline enters here and the air here—see?” “Then what happens?” “Why, they mix into vapor, which passes up through this pipe to the cylinders.” “Oh!” said Bob. “Well, it sounds all right, but I don’t see how that makes the boat go. If I were you I’d stick a mast on her and have some sort of a sail.” “Oh, if the engine gives out,” laughed Nelson, “we’ll put Tommy overboard and let him tow us!” “I mean to learn all about this thing,” said Bob resolutely with a final look at the engine. “How fast did you say she can go, Nel?” “She’s supposed to make eleven and a half miles an hour, but she’s done better than that.” “That doesn’t sound very fast,” said Tom. “It’s fast enough for cruising,” answered Nelson. “Are we all out? Where’s Barry?” He put his head back into the engine room. “Barry, where are you? Oh, I see; sniffing around the ice chest, eh? Well, you’d better wait until to-morrow, if you want anything to eat out of there. Come on!” Nelson locked the doors and the four boys climbed back to the wharf, pausing for a parting look at the _Vagabond_ ere they turned toward home. Possibly you have met these boys before, either at Camp Chicora two summers before, when they came together for the first time and gained the title of the Big Four, or a year later, when in a walking trip on Long Island they met with numerous adventures, pleasant and unpleasant, all of which helped to cement still closer the bonds of friendship, and when they secured an addition to their party in the shape of a wire-haired terrier. If Bob and Nelson and Tom and Dan are already old acquaintances, I advise you to skip the next few paragraphs, wherein, for the benefit of new friends, I am going to introduce my heroes all over again. First of all—if only because he is the oldest—there is Robert Hethington. I call him Robert, though nobody else does, as a mark of respect. He is seventeen years of age, and a full-fledged freshman at Erskine College; and if that doesn’t call for respect, I’d like to know what does! Bob—there! I’ve forgotten already; but never mind—Bob comes from Portland, Maine. He is a very good-looking chap, tall, broad-shouldered, and healthy. He has nice black eyes, somewhat curly black hair, and is at once quiet and capable. Then there is Nelson Tilford, of Boston. He, too, is booked for Erskine in the autumn. In fact, they all are, with the possible exception of Tom. (Tom has just taken the examinations, in spite of the fact that he has only finished his third year at Hillton Academy, and has yet to hear the result.) Nelson is fairly tall, slimly built, lithe and muscular. He isn’t nearly so well-behaved as his thoughtful, sober countenance promises. He is sixteen years old, and has just finished at Hillton.