Another American invention is the switchback. By this plan the length of line required to ease the gradient is obtained by running backward and forward in a zigzag course, instead of going straight up the mountain. As a full stop has to be made at the end of every piece of line, there is no danger of the train running away from its brakes. This device was first used among the hills of Pennsylvania over forty years ago, to lower coal cars down into the Nesquehoning Valley. It was afterwards used on the Callao, Lima, and Oroya Railroad in Peru, by American engineers, with extraordinary daring and skill. It was employed to carry the temporary tracks of the Cascade Division of the Northern Pacific Railroad over the "Stampede" Pass, with grades of 297 feet per mile, while a tunnel 9,850 feet long was being driven through the mountains.