Electric cap lamp approved by U.S. Bureau of Mines
Although electric lighting began to be used in homes by the end of the nineteenth century, the high cost of installing electricity in mines delayed the widespread use of electric lamps in mines until 1915. Two engineers from the U.S. Bureau of Mines, John Ryan and George Deike, played an instrumental role in researching the safety of electric cap lamps. Ryan and Deike founded the Mine Safety Appliance Company in 1914 and, with the help of Thomas Edison, developed electric cap lamps that were less cumbersome, safer, and more light efficient than the safety lamps widely used at the turn of the 20th century. Edison also developed a rechargeable battery that could power the electric cap lamp for 12 hours. The U.S. Bureau of Mines approved the electric cap lamp for use in mines in 1915.