THE MICHIGAN, OR NORTHERN, COAL-FIELD.
coal-field is located in the centre of the State of Michigan, and between Lake Huron and Lake Michigan. Its form and position may be seen on the miniature map of the Alleghany coal-field on page 318. The location of this field is extremely favorable, but its coal-seams are few and thin, and far from productive, as compared with the seams of Ohio or Pennsylvania. They are only two in number, and range from 3 to 5 feet in thickness, but the coal is pure and good. It is generally more bitumi nous in character than the coals of Ohio, and blazes with a bright, strong flame. It is not possible to determine whether the seams developed in Michigan are identical with those of the Alleghany field, from the general depreciation or thinning of the measures in the former field; but it belongs to the great Carboniferous formation of the Appalachian basin, and must, of course, contain the lower seams, if any. The general features and
geology of the country differ only in the topography, which is not so much broken by erosions; but the measures are much thinner here than in the eastern basins. Yet, while the total thickness of the measures is comparatively limited, the coal, nevertheless, lies mostly below water-level, from the topographical evenness of the surface, the horizontal position of the seams, and the fact that the streams have not cut so deep into the measures as in other fields.
The extent of this field is stated at about 12,000 square miles, but the probability is that 6000 would cover the productive area.
But little has been done in the way of practical development in this coal-field, and we presume that 100,000 tons of coal per annum will cover the production.