Suddenly Pratt whispered: "I say, this isn't a tidal river, is it?"
"No; it always flows down," replied Armstrong. "Why?"
"Because----"
And then he stopped.
"Look here," he murmured to Armstrong behind him.
Armstrong looked, and there, at Pratt's feet, was the dark shape of the pram, nestling in its bed of reeds.
"Hang!" exclaimed Armstrong. "We've been going in a circle."
"Just so. Everybody does it!" said Pratt, with a chuckle. "I suspected it when I noticed the way the stream was flowing."
"Nothing to chortle about," Armstrong growled. "We've had all our trouble for nothing. Absolutely waste time!"
"But look how we've enlarged our experience! I think I'd like to be a traveller, like my old uncle. I've read about these circular tours often enough, but never believed in 'em. Why can't one walk straight in the dark?"