THICKNESS.
" Comparative measurements of the thickness of these several deposits of the American coal-fields, indicate a marked reduction from the east towards the west. Those of the Nova Scotia field, as measured at the South Joggins, Bay of Fundy, show a thickness of nearly 3000 feet; those of the southeastern anthracite basin of Pennsylvania, an average thickness about as great; while the central portion of the great Appalachian bitumi nous basin has a depth not exceeding 2500 feet. Those again of the Illi nois basin are probably not thicker than 1500 feet; while the last, the Iowa and Missouri basin, is evidently much shallower, its total depth not surpassing probably 1000 feet.
"In Nova Scotia, the coal-fields contain, in the Joggins section, in all about fifty seams of coal, only five of which, however, are of workable dimensions. These are equivalent to about twenty feet of coal. In the deepest anthracite basin of Pennsylvania, that of Schuylkill, there are, where the formation is thickest, about fifty seams in all; but twenty-five of these have a diameter exceeding three feet and are available for mining.
In the great Appalachian coal-field there appear to be twenty beds in all, and nine or ten of these are of workable size. Again, in the broad basin of Illinois, Indiana, and Kentucky, the total number amounts to eighteen; and it is believed that seventeen of these are of a size Ind quality suitable for mining. Only two or three such are believed to exist in the shallow and much denuded basin of Michigan.
"Still further west, the coal-fields of Iowa and Missouri contain, it is believed, only two or three beds thick enough to be profitable, while the total number of seams of all sizes is probably not more than twelve or th rteen." *