The South Meadow generating station was operated by the Hartford Electric Company in Hartford, CT. The unit described in the 1931 Pop Sci article used 90 tons of mercury in the boiler. The article states that the South Meadow generator produced as much as 143 kWh from 100 lbs of coal, as opposed to an average of 59 kWh from conventional coal fired plants and 112 kWh from exceptionally efficient coal fired plants. The article describes an incident at the plant where a breech of containment from an explosion in the mercury vapor system occurred, releasing mercury and exposing workers to mercury vapor.
The Schiller Mercury Power Station in Portsmouth, NH, is described in this link.