Thomas Curtis Clarke,
The American Railway: Its Construction…
“ Under the old plan he was constantly on guard lest he make a mistake and throw an engine or car off the track. Under the new, his calculations are chiefly about saving time and facilitating the work of the trainmen. Questions of danger rarely come up, being provided against by the perfection of the machinery. By long familiarity with the ground and the ways of [421] handling the trains, the switch-tender in an "interlocking tower" is enabled to safely conduct a score of trains through a labyrinth of switches in the time that the novice would take to make the first move for a single train. ”
