Pierce, The Physical Review, July 1907, March 1909, on crystal rectifiers for electric oscillations.
mercury arc rectifiers were used to convert the incoming 415 volt AC into 220 volts DC.
These were the ones that had mercury arc rectifiers.
Mercury arc rectifiers have now been made totally obsolete by semiconductors, although there are a few still in service in old installations.
Top center are the small rectifiers to supply the field current.