=Summary.=--By way of summary, it may be said that the United States leads the world in coal resources; moreover, its resources are most immediately available, because of their shallow depth and general undisturbed (geologic) condition and their accessibility through railway systems. This is particularly true in the Appalachian region, which contains by far the best coal, is the nearest to the coast, and hence is the most available for ocean trade. On the other hand, the average haul to export points, as already noted, is far greater than that of Great Britain and greater than that of Westphalia; but to offset this the coal has been and can be mined more cheaply than in either Westphalia or Great Britain. The resources of Upper Silesia are large, and the coal is easily mined, but the output will all be needed for central Europe. As regards both quality and quantity, Pennsylvania anthracite is unique; nevertheless, the home needs will continue to be a brake on extensive exports. United States steam and coking coals available for shipment average a little poorer than the corresponding coals of Great Britain, but are superior to the German coals. The total resources of Great Britain, possible, actual, and probable, are only 190,000 million tons, as contrasted with 423,000 million tons in the old German Empire and 3,838,000 million tons in the United States. =Probable Future Production.=--The possible depletion of coal resources is of course important in considering the future, but it can be safely stated that in none of the principal fields now being mined are the resources so depleted that the output therefrom will be reduced for another generation at least. Of the great coal-producing countries, Great Britain, with its increasing rate of production, most nearly approaches the point of ultimate depletion, but that point has been variously placed at one hundred to several hundred years in the future, much depending upon whether with better methods of use the output will continue to increase at the same rate as in the past. Meantime, certain areas in Great Britain with shallower coal beds will be depleted much sooner and the remaining coal will become more and more difficult to get, because of the increasing depth of mining, which in turn will cause a continually increasing cost.