"I read that they start their dams with saplings, which they anchor across
the current with stones. They are much like squirrels, you know, and can
use their fore paws about as well as we can use our hands. I suppose the
stones lose weight by displacing water, but if I hadn't seen these rocks,
I'd never have believed that such big stones could be handled by animals
no larger than beavers."

"See here," said Lew. "These willow branches must have taken root, for
they seem to be growing right up out of the top of the dam. And there's a
birch that's surely growing. You know the branches of some trees will root
if you put them in water, especially willows. Why, if they continue to
grow and take more root, there'll be a hedge of living trees right across
this brook. The dam will become so dense that it will back up a great
quantity of water. I reckon this bottom will just naturally turn into a
swamp after a time."

"Now that's interesting," suggested Charley. "You know the Bible tells us
the world was made in six days; but it seems to me it isn't finished yet.
Every rain washes down soil from the hills and helps to fill up the
valleys and the river-bottoms, and the floods scour out the watercourses
and carry earth and stones down to the ocean. And here we see a piece of
land that used to be fine, dry bottom, now becoming a swamp. It looks to
me as though the earth is changing every day."

They examined the dam more critically. "It's two hundred feet wide if it's
an inch," said Lew, "though the brook isn't more than fifteen or twenty.
You see, it extends on each side of the brook to land that is a little
higher than the level of the stream bank. That's what makes this big head
of water. At the least there are several acres of it."