In less than an hour they found themselves in the very heart of the forest. Great trees grew on all sides of them, and the monstrous roots were anything but easy to climb over. In one spot were thick masses of vines, utterly barring their further progress in that direction.
"Say, I don't like this!" exclaimed Bob at last. "This forest is getting thicker and thicker."
"Just my idea," answered Mark. "I thought we would be through to the other side before this."
"It's wider than I imagined. Perhaps it keeps on for miles, Mark."
They came to a halt, not knowing exactly what to do. Then Mark scratched his head.
"Shall we go back, Bob?"
"Not if we can reach that river by going ahead."
"It's pretty dark under these trees."
"So it is."
"Do you know which is west, now that the sun has gone under a cloud?" went on Mark seriously.