steep bank afforded special
facilities for shore burrows.

The explorer's fever being now hot upon him, the Boy could not stay to
examine this pond minutely. He pressed on up-stream with breathless
eagerness, thrilling with expectation of what the next turn might
reveal. As a matter of fact, the next turn revealed nothing--nor the
next, nor yet the next. But as the stream was full of turns in this
portion of its course, that was not greatly discouraging.

About a quarter of a mile, however, above the head of the narrow pond,
the ardent explorer came upon a level of sparse alder swamp. Here he
found the stream just beginning to spread over its low banks. The
cause of this spreading was a partial obstruction in mid-channel--what
looked, at first glance, like an accidental accumulation of brush and
stones and mud. A second look, however, and his heart jumped with
excitement and delight. Here was the beginning of a new pond, here
were the foundations of a new dam. He would be able to see what few
indeed of the students of the wilderness had had the opportunity to
watch--the actual process by which these wilderness engineers achieved
their great work.

All about the place the straightest and brushiest alders had been cut
down, those usually selected being at least ten or twelve feet in
height. Many of them were still lying where they fell; but a number
had been dragged to the stream and anchored securely, with stones and
turfy clay, across the channel. The Boy noted, with keenest
admiration, that these were all laid with the greatest regularity
parallel with the flow of the current, butts up stream, brushy tops
below. In this way, the current took least hold upon them, and was
obstructed gradually and as it were insidiously, without being
challenged to any violent test of strength. Already it was lingering
in some confusion, backing up, and dividing its force, and stealing
away at each side among the bushes. The Boy had heard that the
beavers were accustomed to begin their dams by felling a tree across
the channel and piling their materials upon that as a foundation. But
the systematic and thorough piece of work before him was obviously
superior in permanence to any such slovenly makeshift; and moreover,
further to discredit such a theory, here was a tall black ash close to
the stream and fairly leaning over it, as if begging to be put to some
such use.

At this spot the Boy stayed his explorations for the day. Choosin