They are also seen as a conduit between this world and other-than-human spheres, and were thus used as such by the Navajo hero Whirling Logs.  
Powerful and mysterious to Native American peoples, Southeastern tribes saw them as a sign that a girl was menstruating for the first time or that something evil was about to happen; while walking through one was thought to confer healing powers on a medicine man. They are also seen as a conduit between this world and other-than-human spheres, and were thus used as such by the Navajo hero Whirling Logs.  For 10 points, what is this natural phenomenon, the colors of which children were cautioned not to count, lest their fingers become crooked or fall off?
Powerful and mysterious to Native American peoples, Southeastern tribes saw them as a sign that a girl was menstruating for the first time or that something evil was about to happen; while walking through one was thought to confer healing powers on a medicine man.
Rainbows