A mule and mule driver in a coal mine. Mules - many spending their entire lives in a mine - were a common means of transporting coal and workers in the 19th and early 20th centuries. Drivers usually named the animals to reflect their disposition, such as Sparky or Pokey. They also sang a common tune called "My Sweetheart's the Mule in the Mine," reflecting the amount of time they spent with mules.
