Of this coal area, Persifor Frazier, Jr., says: "Those beds which occur on the east flank of the Rocky Mountains have been followed for five hundred miles and more, north and south; and if it be true that these are 'fragments of one great basin, interrupted here and there by the upheaval of mountain chains, or concealed by the deposition of newer formations,' then their extension east and west, or from the eastern range of the Rocky Mountains or Black Hills to Weber Canyon, where an excellent coal is mined, will fall but little short of five hundred miles. Throughout this extent these beds of coal are found between the upper cretaceous and lower tertiary (or in the transition beds of Hayden), wherever these transition beds occur, whether on the extreme flanks or in the valleys and parks between the numerous mountain ranges. Assuming that the eroding agencies together have cut off one-half of the coal from this area, and taking one-half of the remainder as their average longitudinal extent, we have over fifty thousand square miles of coal lands, accounting the latitudinal extent as only five hundred miles; whereas we have no reason to believe that it terminates within these bounds, but, on the contrary, good reason for supposing that it extends northward far into Canada, and southward with the Cordilleras. All this territory has been omitted in the estimate of the extent of our coal fields." DISTRICTS CONTIGUOUS TO THE PLAINS. The reader has now had the salient features of the great plains placed before him in succession. The more interesting districts immediately adjoining will well repay the reader for a brief consideration. THE NORTH PLATTE DISTRICT. A late writer, who has studied the country of which he speaks very closely,[6] thus describes the North Platte District: [6] Dr. H. Latham, under date June 5th, 1870, in the Omaha Daily Herald. "The distance from the mouth of the North Platte, where it joins the South Platte on the Union Pacific Railroad, to its sources in the great Sierra Madre, whose lofty sides form the North Park, in which this stream takes its rise, is more than eight hundred miles. Its extreme southern tributaries head in the gorges of the mountains one hundred miles south of the railroad, and receive their water from the melting snows of these snow-capped ranges. Its extreme western tributaries rise in the Wahsatch and Wind River ranges, sharing the honor of conveying the crystal snow waters from the continental divide with the Columbia and Colorado of the Pacific. Its northern tributaries start oceanward from the Big Horn Mountains, three hundred miles north of the starting-point of its southern sources. "It drains a country larger than all New England and New York together. East of the Alleghany Mountains there is no river comparable to this clear, swift mountain stream in its length or in the extent of country it drains.