From the July 25, 1931, issue

98-TON BUTTERFLY VALVE, A SIMPLE DEVICE

A good place for a photographer to take a picture, this penstock will be serving an even better purpose when it begins to carry water through the dam to turn the huge turbines of the Ruskin power plant, British Columbia.

The flow of water through this 19-foot-diameter intake pipe is controlled by the butterfly valve just behind the workman in the photograph.