English: A mule at the Experimental Mine, which opened in 1910, Bruceton, Pennsylvania. According to the CDC/NIOSH website: "In 1910, the newly created U.S. Bureau of Mines leased a 38-acre tract of land from the Pittsburgh Coal Co. in Bruceton, about 13 miles south of Pittsburgh. Here, a new mine, known as the Experimental Mine, was opened. One of the early experiments in the Experimental Mine demonstrated that coal dust by itself was capable of propagating an explosion even in the absence of any methane gas. This demonstration was contrary to the old belief widely held at the time that coal dust could not explode without gas. This view had led to the very dangerous and widespread practice of using loose coal dust in mines to pack explosives in boreholes, which had cost many thousands of lives. These early experiments clearly proved that such a practice was too hazardous to continue."[1]