Edward Whymper,
Scrambles amongst the Alps — Chapter 20
(1871)
“ They object sometimes, because they think it is unnecessary. Crevasses that are bridged by snow are almost always more or less perceptible by undulations on the surface; the snow droops down, and hollows mark the courses of the chasms beneath. An experienced guide usually notices these almost imperceptible wrinkles, steps one side or the other, as the case may require, and rarely breaks through unawares. Guides think there is no occasion to employ a rope because they think that they will not be taken by surprise. ”
