whistle treadle

A steamboat whistle was blown by pressing down on a treadle, usually located to the right of the pilot wheel. On a triple-chime whistle, the first downward pressure on the treadle brought out the first note, and more pressure produced the second note. Flooring the treadle brought out the full-throated chord that shook the pilothouse and left the blower a bit deaf. It was a thrill to those on shore to hear the whistle of a steamboat, but the thrill was even greater when experienced in the pilothouse.