The second experiment in underground gasification of coal at Gorgas was operated continuously for 22-1/2 months without any great difficulty. As shown in figure 1, the initial development consisted of 1,100 feet of double entry between borehole II and the entry seal driven horizontally in the coal bed and a single entry 300 fee long connecting borehole II with borehole I. Theses entries provides a passage for the gas-making fluids along the coal faces. Five large-diameter boreholes on 300-foot centers were drilled from the surface to the entries, and subsequently two additional large-diameter boreholes were drilled near the perimeter of the reacting zone in order to introduce air at the horizon of the coal bed and to remove gas and products of combustion. An air black of approximately 7.500 c.f.m. usually was employed, but at times a reduced blast rate was used. The operational characteristics of the installation were studied, and records were kept of the volume of air admitted to the system, temperatures at various points underground, and other pertinent data.