"The wind has almost died out," said Hop, as he looked about him. "Not much!" replied Ash. "When you are running in a boat before the wind, there seems to be little or no breeze," said Dory, who did not abandon his function as instructor. "When you ride in a carriage in a hot day, with the wind, you feel the heat. So in a boat. I have been nearly roasted on the lake in this boat when I was going before the wind, while it would be comfortably cool on the wind. The motion of the boat kills the breeze. Some boatmen make Hop's blunder, and put on more sail than they can bear; and then it is a dangerous error." "Haul in on the main-sheet! A pull on the lee jib-sheet!" said Ash, when the Goldwing came to a bend in the river, which made it necessary to brace up the boat a little more. After the change of course, the breeze came fresher; and Hop realized his mistake, by experience. The sloop went rapidly down the river with the wind about on the beam, or across the width of the boat, and out into the lake. The waves were lively there; and they were short and choppy, giving the boat a jerky motion. "I suppose you know where the bottom is, out here, Ash," said Dory. "I think I do; and it is pretty near the top of the water for a mile. I shall hold her on her present course till we have made about that distance from the mouth of the river." "About half a mile from the point will cover it, but it is best to be on the safe side. When Diamond Island shuts in Split Rock Light, you are all right for any course except south," added Dory. "I suppose nobody but Ash is expected to understand that remark," said Archie. "Shuts it in!" "In other words, when you can see Split Rock Light over Diamond Island, you are far enough from the shore to avoid the shoals off Field's Bay," Dory explained. "I can understand that," added Archie. "If the light were not more than two feet above the water, we could not see it all when we come to the position described, for it would be shut in. I have about two hundred ranges written down in a book at home, and this is one of them. Sometimes they put two lighthouses on a shore. If one shut out the other, you could tell, in one case, how far north you had gone. When I am going into the river with the Sylph, I don't run in till I have brought the tip of the point in range with the white chimney on Paucett's house. The more of these ranges you learn, the better you will be qualified to sail a boat on Lake Champlain." It was nearly dark when the Goldwing returned to the school; but every member of the class had taken his turn in sailing the boat, and each thought he knew as much as Dory about it. CHAPTER XXX. THE GOLDWING'S TRIP TO PLATTSBURG.