Interior of the Butte Hoist Plant, showing the row of synchronous electric motors, each connected to the reciprocating air compressor it drives. A reciprocating compressor works just the opposite of a reciprocating engine. Mechanical power delivered by the motor drives a piston rod back and forth, and each stroke of the piston compresses a batch of air, sending it to the receivers. | Source: Butte-Silver Bow Public Archives, Smithers Collection, photo no. 40.060.07.
