National Geographic : 1936 Jul
A MOMENT'S BREATHING SPACE PRECEDES THE MAD PLUNGE With bodies tense the boatmen "ease" into the chosen channel. Snow Hole Rapids, which fall 10 feet in 150, give thecrew some oftheir most anxious moments. A few inches too far to the right or left might spell disaster (page 112). Sweeps have no sculling action at all; they areused merely forsteering. Unlike arudder, they are held above the surface except when needed to sweep the craft clear of an object or keep it on the course.No power was provided fortheboat; itsimply floated downstream with the current.