along the major synclinal trough which extends eastward from Fort Smith through Crawford, Sebastian, Franklin, Johnson, and Logan counties to the vicinity of Russellville, Pope county, a distance of about seventy-five miles. This area is about twenty miles wide and decreases in width toward the eastern end. The remainder of the developed coal field extends south of Fort Smith into southern Sebastian and northern Scott counties. In addition, coal is found in other relatively small areas in the Arkansas River Valley region north of the Ouachita Mountains. These areas are, however, usually widely separated and occupy the topographically prominent points of the Arkansas Valley, such as Magazine Mountain, Petit Jean Mountain, and Mount Nebo, and do not constitute any important part of the coal lands of the State.

The area of workable coal lands within the State is estimated at between 300 and 350 square miles and the total area covered by coal measure beds at about 1,620 square miles.

General Geology

The coal-bearing formations of Arkansas are confined to the lower part of the Pennsylvanian series of beds which in Oklahoma is usually classified as the McAlester shale. This formation has, in Arkansas, been divided into the Spadra shale, the Fort Smith formation, and the Paris shale. These three formations make up a total thickness of about 1,700 feet and are underlaid by the Pennsylvanian Hartshorne sandstone and Atoka shale which together have a thickness varying from 1,800 to 6,000 feet or more. The Atoka shale carries some coal, but the seams are usually only a few inches thick and coal mined from them is consumed locally.

As in Oklahoma, by far the larger coal production of Arkansas has come from the top of the Hartshorne sandstone and is known as Hartshorne coal. This probably makes up 99 per cent of the Arkansas output. The upper portion of the Fort Smith formation has been mined for coal near Charleston, Franklin county, and produces "Charleston" coal, and the middle of the Paris formation is mined near Paris, Logan county, and produces "Paris" coal.

*U. S. Geological Survey Bulletin 326, "The Arkansas Coal Field," by A. J. Collier.

The coal measure beds are made up of sandstones and carbonaceous shales, the shales predominating by a large margin. Limestones, dolomites and hard calcareous beds are conspicuously

absent.

The structural conditions found in the coal fields are very largely responsible for the distribution of the coal and the economic importance of the beds. The formations making up the Arkansas River Valley, occupying as they do the lowest portion of the regional syncline, have been considerably folded, twenty-three major anticlines having been mapped in the coal-bearing area. This folding is reflected in the topography of the region by numerous east-west ridges which usually rise about 75 or 100 feet above the valley floor. Many of these are twenty miles or more in length. Many of these folds have been eroded and faulted and this condition has not infrequently been the cause of the termination, discontinuity, and thinning out of the seams and has been a contributing factor to the cost of mining. These features have also been largely responsible for the division of the field into a series of separated mining districts.

The coal increases in hardness in a fairly consistent manner from the western Arkansas line eastward, and contains about three to six times as much fixed carbon as volatile combustible matter in the western portion and from seven to nine times as much in the eastern. It thus grades from bituminous through semi-bituminous to a semianthracite. About 15 per cent of the coal produced is semi-anthracite. The following table shows the increase in the ratio of the fixed carbon to the volatile combustible matter in the coal from the west end of the field to the east.

One of the most commonly used classifications of coal is that proposed by P. Frazer, Jr. This is based on the relation between the amount of fixed carbon and the volatile combustible matter (fuel ratio) in the coal, and is given as follows:

Thus, an anthracite is a coal containing more than 12 times as much fixed carbon as volatile combustible matter, etc. This table does not provide for lignite which has a fuel ratio of less than 1. As understood by the trade, the limits are usually somewhat lower than these given.

Arkansas "anthracite" coals have fuel ratios from about 6.5 to 8.5, semi-bituminous from 4.5 to 6.5, and bituminous usually about 3.

The following table' gives a series of analyses according to the U. S. Geological Survey Fuel Testing Plant.

Laboratory coking tests made with Arkansas coals have indicated that some of the coals would probably coke. In practice, most of the Arkansas coals seem to be naturally non-coking, although it has been determined that the coals can be made into coking coals by the addition of pitch. U. S. Geological Survey tests show that Jenny Lind coals will make good coke in practice when mixed with 8 per cent pitch.

'Briquetting tests with Arkansas coals carried out by the U. S. Geological Survey have indicated that when 6 to 10 per cent pitch is added to slack coal that it can be made into high grade fuel.