The carboniferous measures are the highest and latest geological formation in the great coal fields of the United States. Therefore where the strata have not been disturbed by flexure the coal seams lie near the surface. This is generally the case in the bituminous districts, and it is also partially true in the northern anthracite coal field. Deep mining is necessary only in the middle and southern anthracite coal fields, where the folds are close and precipitous, and the deep and narrow basins formed by them have been filled with deposits of a later geologic age. Some of the difficulties to be met and overcome in mining coal will by this time have been appreciated by the reader. But some of them only. The inequalities of roof and floor, the pitching seams, the folds and faults and fissures, all the accidents and irregularities of formation and of location, make up but a few of the problems which face the mining engineer. But the intellect and ingenuity of men have overcome most of the obstacles which Nature placed in the way of successful mining when she hardened the rocks above her coal beds, crowded the earth’s crust into folds, and lifted the mountain ranges into the air. It will not be out of place at this time to make mention of those localities in which coal is found. Indeed, there are few countries on the globe in which there are not carboniferous deposits of greater or less extent. Great Britain, with Ireland, has about 12,000 square miles of them. In England alone there is an area of 8,139 square miles of workable coal beds. In continental Europe the coal fields are numerous, but the character of the deposit is inferior. Coal is found also in the Asiatic countries, in Australia, and in South America; and in Nova Scotia and New Brunswick there is an area of 18,000 square miles of coal measures. The combined areas of coal measures in the United States amount to about 185,000 square miles. The Appalachian or Alleghany region contains about 60,000 square miles, included in the States of Pennsylvania, Virginia, West Virginia, Maryland, Ohio, Kentucky, Tennessee, Georgia, and Alabama. The Illinois and Missouri region contains also about 60,000 square miles, and has areas not only in the States named, but also in Indiana, Iowa, Kentucky, Kansas, and Arkansas. Michigan has about 5,000 and Rhode Island about 500 square miles. There are also small areas in Utah and Texas, and in the far West there are workable coal fields in Colorado, Dakota, Indian Territory, Montana, New Mexico, Washington, Wyoming Territory, Oregon, and California. The entire coal area of the United States, with the exception of that in Rhode Island and a few outlying sections in Pennsylvania, contains coal of the bituminous variety only. Both the area and supply are therefore practically without limit. In the coal regions of Rhode Island the disturbances affecting the earth’s crust have been very violent. The motion, heat, and compression have been so