The lungs of the machine--its engines--are the crux of man's mechanical wisdom and skill. Their marvelous reliability and intricacy are almost as awesome as the human anatomy. When both engines are going well, and synchronized to the same speed, the roar of the exhausts develops into one long-sustained and not inharmonious _boom-m-m-m-m!_ It is a song of pleasant melody to the pilot, whose ear is ever pricked to catch the first semblance of a "sharp" or "flat" note telling him that one or more of the twelve cylinders of each busy engine is missing fire and needs a little doctoring. It was about four o'clock that afternoon when our party first sighted the low, out-jutting sea-coast of Florida. As they came slowly toward it, by reason of their angular course of approach, they could gradually make out a group of green palms here and there along the white stretches of sand, and see clusters of light-colored buildings, piers, shipping, and people moving about. Thus they passed Juno and Palm Beach, and then saw the thicker cluster of fine dwellings of Miami itself, the most southerly city on the Florida mainland. Paul was guiding the Sky-Bird at this time, and turned her across the limpid waters of Biscayne Bay, cutting a huge circle above the town and slowly swooping downward toward the broad white beach, as he picked out a level stretch for landing. Townspeople who had been watching the strange airplane, so much like a great bird, now ran forward to see it land. A moment later, with a graceful drop and upward curve, it struck the sandy beach and ran forward lightly until the brakes were applied and it was brought to a standstill. CHAPTER XII FIGHTING A DEVIL-FISH Many questions were asked our friends by the onlookers, but they gave them evasive replies, being careful to let out no hint as to their real identity and connection with the approaching race around the world. Two husky negroes were engaged to watch the airplane until relieved from such responsibility, and Mr. Giddings then led the boys to the home of a Mr. Choate, a close and trusted friend and superintendent of the big Miami Aquarium, one of the most noted repositories for live fish in the country. Mr. Choate was astonished beyond measure when he learned that his old friend had come in the big airplane which he and his wife had noticed over the town a short time before, and was still further surprised when Mr. Giddings bound him to secrecy and told him that the young men with him constituted the crew of one of the two airplanes which was so soon to circle the earth by way of the equator. He shook hands warmly with them, and with his charming wife made them all very much at home.