a farewell cheer, and
in a few moments they were hid from sight by the Third Avenue Bridge.
The tide was against them, but the day was a cool one for the season,
and the boys rowed steadily on in the very best of spirits. There was a
light south wind, but as there were several bridges to pass, Harry
thought it best not to set the sail before reaching the Hudson River. It
required careful steering to avoid the steamboats, bridge piles, and
small boats; but the _Whitewing_ was guided safely, and her signal--a
red flag with a white cross--floated gayly at the bow.

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 ro