The passengers on the boat waved as they drifted by. Why is that those afloat always feel so impelled to wave at people they have never met? "How far to Philadelphia," we shouted across to the man in uniform who stood at the helm of the vessel.

"Not far," he called back. "You're almost there. Just stick to the bank and you'll see it on your left." The onward journey was a bit of a scramble, as we followed the waterway on through meadows and forests, but by nightfall we had reached Philadelphia.

But this is not the great city founded by William Penn on the banks of the Delaware river.