Uncle John had made one serious mistake: he had forgotten all about the tide, and never thought of the difficulty the boys would find in passing Farmers-bridge with the tide against them. They had passed High Bridge, and had entered a part of the river with which the boys were not familiar, when Joe Sharpe suddenly called out, "There's a low bridge right ahead that we can't pass." A few more strokes of the oars enabled Harry to see a long low bridge, which completely blocked up the river except at one place, that seemed not much wider than the boat. Through this narrow channel the tide was rushing fiercely, the water heaping itself up in waves that looked unpleasantly high and rough. The boat was rowed as close as possible to the opening under the bridge; but the current was so strong that the boys could not row against it, and even if they had been able to stem it, the channel was too narrow to permit them to use the oars.
Harry ordered the boat to be rowed up to the bridge at a place where there was a quiet eddy, and all the crew went ashore to contrive some way of overcoming the difficulty. Presently Harry thought of a plan. "If we could get the painter under the bridge, we could pull the boat through easy enough if there was nobody in her."
"That's all very well," said Joe, "but how are you going to get the painter through?"
"I know," cried Jim. "Let's take a long piece of rope and drop it in the water the other side of the bridge. The current will float it through, and we can catch it and tie it to the painter."
The plan seemed a good one; and so the boys took a piece of spare rope from the boat, tied a bit of board to one end of it for a float, dropped the float into the water, and held on to the other end of the rope. When the float came in sight below the bridge they caught it with the boat-hook, and throwing away the piece of board, tied the rope to the painter. "Now let Joe Sharpe get in the bow of the boat, to keep her from running against anything, and we'll haul her right through," exclaimed Harry.
Joe took his place in the bow, and pushing the boat off, let her float into the current. Then the three other boys pulled on the rope, and were delighted to see the boat glide under the bridge. Suddenly Joe gave a wild yell. "She's sinking, boys!" he cried: "let go the rope, or I'll be drowned!" The boys, terribly frightened, dropped the rope, and in another minute the boat floated back on the current, half full of water, and without Joe. Almost as soon as it came in sight, Harry had thrown off his shoes and jumped into the river.