the author feels that there are inaccuracies, as many companies can not agree upon a classification of their own, much less with one used by their neighbors. There is still considerable confusion in the Plymouth, Nanticoke, Glen Lyon, and Mocanaqua districts of the Northern field (figs. 1 and 3), and a great deal of information is needed as to the Southern field (figs. 2 and 4), for development already done has not sufficed to determine the extent of each bed. In the Forest City, Carbonate, Jermyn, and Priceburg districts of the Northern field (fig. 3) it has been customary to call the top bed the "surface" or the "top" bed. These names have been omitted, because they can be applied, if proper localities are selected, to virtually all beds in these districts, and to show them on the chart would be confusing. In the charts the nomenclature suggested by the Second Geological Survey of Pennsylvania was adopted in preference to a name system for the beds. This nomenclature is familiar to many engineers in the anthracite region, whereas a name system might be confusing, as beds that have the same name may lie at different geological horizons. The tables on preceding pages have shown the importance of thin-bed mining in the anthracite region, and the correlation charts show the large number of beds that are less than 5 feet thick. In the Northern field 106 of the 177 measurements of beds shown are less than 5 feet, in the Eastern Middle field 16 of 32 are less than 5 feet, in the Western Middle field 34 of 71 are less than 5 feet, and in the Southern field 61 of 92 are less than 5 feet. CHANGE IN THICKNESS OF BEDS In future the production from the thin beds will continue to increase, and the minimum thickness of the beds that will be considered workable will decrease, if past history repeats itself. Not long ago beds less than 5 feet thick were considered unworkable; to-day in a few places the coal companies are working beds less than 2 feet thick. Some companies now have in mind the working of beds having an average thickness of only 20 inches, and a short time ago an independent company whose mine is nearing exhaustion inquired as to the possibility of working a bed only 17 inches thick. MINING CONDITIONS A number of conditions that vitally affect mining methods will be briefly discussed before the mining methods are considered. Many of these conditions are geological, others have resulted from lapse of time, and others are the outcome of the mining methods used. Both of the latter two might be chargeable to lack of foresight when first the author feels that there are inaccuracies, as many companies can not agree upon a classification of their own, much less with one used by their neighbors. There is still considerable confusion in the Plymouth, Nanticoke, Glen Lyon, and Mocanaqua districts of the Northern field (figs. 1 and 3), and a great deal of information is needed as to the Southern field (figs. 2 and 4), for development already done has not sufficed to determine the extent of each bed. In the Forest City, Carbonate, Jermyn, and Priceburg districts of the Northern field (fig. 3) it has been customary to call the top bed the "surface" or the "top" bed. These names have been omitted, because they can be applied, if proper localities are selected, to virtually all beds in these districts, and to show them on the chart would be confusing. In the charts the nomenclature suggested by the Second Geological Survey of Pennsylvania was adopted in preference to a name system for the beds. This nomenclature is familiar to many engineers in the anthracite region, whereas a name system might be confusing, as beds that have the same name may lie at different geological horizons. The tables on preceding pages have shown the importance of thin-bed mining in the anthracite region, and the correlation charts show the large number of beds that are less than 5 feet thick. In the Northern field 106 of the 177 measurements of beds shown are less than 5 feet, in the Eastern Middle field 16 of 32 are less than 5 feet, in the Western Middle field 34 of 71 are less than 5 feet, and in the Southern field 61 of 92 are less than 5 feet. CHANGE IN THICKNESS OF BEDS In future the production from the thin beds will continue to increase, and the minimum thickness of the beds that will be considered workable will decrease, if past history repeats itself. Not long ago beds less than 5 feet thick were considered unworkable; to-day in a few places the coal companies are working beds less than 2 feet thick. Some companies now have in mind the working of beds having an average thickness of only 20 inches, and a short time ago an independent company whose mine is nearing exhaustion inquired as to the possibility of working a bed only 17 inches thick. MINING CONDITIONS A number of conditions that vitally affect mining methods will be briefly discussed before the mining methods are considered. Many of these conditions are geological, others have resulted from lapse of time, and others are the outcome of the mining methods used. Both of the latter two might be chargeable to lack of foresight when first GEOLOGY OF ANTHRACITE KEGION In many parts of the anthracite region one can find two beds separated by a small parting. This condition immediately causes trouble, for the parting may be of such a character that one bed can not be mined before the other and a reasonable recovery made from the second mined bed. The parting may be small, yet economical mining of the two beds at the same time may not be possible, as the expense of handling the rock may be too great. One bed may have contained a particularly high grade of coal, whereas the other bed may have been of a poorer quality that was unmarketable when the first bed was mined. Examples of mining under the difficult conditions that exist are discussed later. From a point on the Susquehanna River near Pittston to a point below Nanticoke, a distance of about 18 miles, extends the so-called Buried Valley of the Wyoming. This valley is about 1 mile wide at its widest part, is 50 to 350 feet deep, is filled with water-bearing glacial drift, and contains large amounts of quicksand. Coal beds often outcrop in this valley, and their mining is exceedingly dangerous. It is unsafe to approach too close to the outcrop or even to mine the beds unless the cover is thick enough to make mining safe. Furthermore, the roof must be permanently supported to forestall danger of breaking, for in that event there would be inrushes of water, the mine workings would be flooded, and the lives of the men would be in danger. Up to the present, therefore, no second mining or longwall work has been attempted in this area. INFLUX OF WATER Another feature which influences the mining methods used to some extent is the amount of water to be handled. A survey of the whole anthracite region showed that 10.9 tons of water have to be handled for each ton of coal mined. LACK OF INFORMATION The meager information the various operators possess on the working of thin beds by other companies has greatly retarded the development of thin-bed mining. Most of the new methods used in the anthracite field have been developed at individual collieries, and occasionally the data that have been obtained at one colliery of a company have not been utilized at another colliery of the same company when a similar bed was opened. Until an exchange of ideas between engineers of different companies is established present-day conditions will probably continue. A concerted drive for better mining methods, rather than improve |