At length I was afraid, should we get closer, that we might make some noise and alarm the animals.  I therefore made a sign to my companions to stop; and looking down, we could discern one of the dams I have spoken of carried across the stream from one side to the other, and apparently not quite finished.  Though several beavers were running about it, they were not at work; indeed, all their operations are carried on during darkness.  Nature, of course, has given them the instinct to work at this time, which saves them the destruction that would otherwise probably overtake them, both from men and beasts.