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1970-1979 tivity. Jeffrey Mining Machinery Co. devel- oped a digitally coded FM radio-control system that would permit two or more machines to operate simultaneously and prevents one transmitter unintentionally operating the wrong machine. A March 1975 Coal Age article, "Boost Your Productivity by Adding Continuous Miners," written by Stan Suboleski, an instructor at Penn State, explained the ratio- nal for operating two continuous miners in one production heading. The technique offers the promise of nearly doubling present tonnage rates with about one-half of the cap- ital and manpower required for a complete new section. This method of room-and-pillar mining would become very popular and eventually be known as a super section. Another article, "The Yardstick of Productivity…," (July 1975) asks, "Is it high tons per man-day or is it low cost per ton?" The author, who is advocating high horse- power over manpower, explained that the answer is both. The graphic provided depicting major technological eras in underground mining does not yet include longwall mining. The new health and safety laws gave new impetus to the interest in longwall mining. The absence of the need for rock dusting, the ease and efficiency of ventilation, good and almost automatic roof control with little consumable material appeared the chief attractions. *Coal Age,July 1975 Longwall units pro- duced greater ton- nages in the 1970s and more were deployed the following year. In the March 1971 issue, Brian Watson, a long- wall engineer formerly of Bethlehem Mines, reported on improved operations at the com- pany's No. 33 mine, Cambria Division, "where a longwall unit recently broke a world production record by mining 7,280 tons in a 24-hr period. The best shift pro- duction during this period was more than 2,860 tons. In the May 1971 issue, William Laird, vice president of engineering at Eastern Associated Coal Corp. reported on his company's continuing usage and develop- ment of longwall mining technologies. The first company to install and success- fully operate such a system in the Pittsburgh seam, in 1969 Eastern began longwall mining in its Federal No. 1 mine near Grant Town, W.Va. Operated by a seven-member crew, the highest shift ton- nage was approximately 2,500 tons. In the August 1972 issue, Coal Age pub- lished the forerunner to the annual Longwall Census. Written by Joseph Kuti, chief engi- neer at Mining Progress, he reported that as of April 1972, 41 longwalls were operating or delivered in the U.S. Sixteen of the 41 units were plows and 25 were shearers. At the time, 22 more contracts had been placed for additional longwall systems. Nine of those new contracts called for plows and 14 for shearers. Nationwide, the longwall leader was Eastern Associated Coal. By 1972, they 132 www.coalage.com 100th Anniversary Special Issue August 2012