The Holyoke Water Power Testing Flume was designed by engineer Clemens Herschel and installed between the First- and Second-level canals near Cabot Street. The flume was used to test the performance of the water turbines that powered mills and factories. The testing procedure developed in Holyoke became an industry standard. In this image, five men stand near the flume, another turns the screw that powers the flume and another sits and reads. The fifth man from the left, wearing a jacket and vest with a watch fob, is believed to be Clemens Herschel. The chalkboard on the wall has the date "Sept 21, 1888."