dth, it was built with a
certain looseness and elasticity for which he was at a loss to
account. Presently he observed, however, that this dam had no place of
overflow for letting off the water. The water stood in the pond at a
height that brought it within three or four inches of the crest. At
this level he saw that it was escaping, without violence, by
percolating through the toughly but loosely woven tissue of sticks and
twigs. The force of the overflow was thus spread out so thin that its
destructive effect on the dam was almost nothing. It went filtering,
with little trickling noises, down over and through the whole lower
face of the structure, there to gather again into a brook and resume
its sparkling journey toward the sea.

The long upper slope of the dam was smoothly and thoroughly faced with
clay, so that none of its framework showed through, save here and
there the butt of a sapling perhaps three or four inches in diameter,
which proclaimed the solidity of the foundations. The lower face, on
the other hand, was all an inexplicable interlacing of sticks and
poles which seemed at first glance heaped together at haphazard. On
examination, however, the Boy found that every piece was woven in so
firmly among its fellows that it took some effort to remove it. The
more he studied the structure, the more his admiration grew, and his
appreciation of the reasoning intelligence of its builders; and he
smiled to himself a little controversial smile, as he thought how
inadequate what men call instinct would be to such a piece of work as
this.

But what impressed him most, as a mark of engineering skill and sound
calculation on the part of the pond-people, was the direction in which
the dam was laid. At either end, where the water was shoal, and
comparatively dead even in time of freshet, the dam ran straight,
taking the shortest way. But where it crossed the main channel of the
brook, and required the greatest strength, it had a pronounced upward
curve to help it resist the thrust of the current. He contemplated
this strong curve for some time; then, a glance at the sun reminding
him that it was near noon, he took off his cap to the low-domed house
in the water and made haste back to camp for dinner.

CHAPTER III

In the Under-water World

MEANWHILE, in the dark chamber and the long, dim corridors of the
House in the Water there was great perturbation. The battle with the
otter had been a tremendous episod