OHIO 735 it, and consequently is now cut down to a lower level than they. In other words, the axis has been converted into a basin. The Clinton Limestone generally rises in a terrace-like outcrop around the margin of the eroded Cincinnati beds, and its base is marked by the finest line of springs in the State. In its most characteristic phases it is a crystalline limestone that takes a good polish. In very many localities it yields small quantities of petro leum, which seems to be indigenous. The supply is too limited to be valuable. The Niagara group, also of Upper Silurian age, is of much greater thickness and of proportionally greater economic and scientific importance than the Clinton limestone. As at the Falls, it here consists of a stratum of shale overlain by a massive limestone. It forms the surface rock for about 3000 square miles, but through much of this area it is concealed by heavy beds of Glacial Drift, by which its importance as a factor in the topography and the eco nomic geology of the district is much reduced. In composition the limestone is almost a typical dolomite, but it is still fossiliferous, the fossils occurring as internal casts. It contains a large and in teresting fauna. From near the base of the Niagara beds the "Dayton" stone, one of the most valuable building stones of the State, is derived. The formation yields excellent building stones at other horizons also, and its upper beds furnish lime. The Lower Hcldcrbcrg Limestone occupies even a wider area as a surface formation than the last-named, but is largely covered with Drift deposits. There are whole counties of which it is known to constitute the rocky floor, in which it does not once rise to the surface. It is seen to the best advantage in the north of High land county, where it yields a remarkably even -bedded building stone. Like the Niagara Limestone, it is a dolomite in composi tion. It is poor in fossils, but the few that it contains are highly characteristic. The transition from Upper Silurian to Devonian time which is made in ascending to the next stratum in the scale, the Corniferous Limestone, is accomplished without any structural break or irregu larity, but there is an abrupt lithological change, the latter stratum being a true carbonate of lime, and an abundant and pronounced Devonian fauna appears in its very lowest beds. The Corniferous Limestone forms a narrow belt on each side of the axis, from central Ohio northward, but by the overlap of the next succeeding formations it is entirely lost in southern Ohio. Even where it constitutes the highest bedded rock it is largely obscured by Drift deposits. At Kelly s Island, Sandusky, Marion, Delaware, and Columbus it is largely worked for building stone, lime, and fur nace flux. The earliest vertebrate remains of the Ohio scale are found in this stratum. The box-like skull of a large ganoid fish, Macropctalichthys sulliva/iti, Newberry, occurs near the base of the series, and the teeth and bones of other ganoids and selachians are frequently met with in the higher beds. In the State quarries at Columbus these remains constitute a veritable bone bed, a layer 4 to 6 inches in thickness being in large part composed of them. A heavy deposit of black shale, the Ohio Shale of the table, and the Huron shale of Newberry, directly overlies the Corniferous Limestone in northern and central Ohio, and extends across the State from north to south. It is composed of two black shales, the Cleveland and the Huron, including a blue shale, the Erie, be tween them. The latter is 1200 feet thick in north-eastern Ohio, but rapidly wedges out as it is followed westward to the axis, and the Cleveland and Huron seem here to be welded into one mass. The black shale contains an average of 8 or 10 per cent, of bituminous matter, a chief source of which is found in a resinous disk of microscopic size that exists in the shale in immense num bers, which Dawson has named Sporangites huronensis. Apart from this minute form the shale is almost barren of fossils, but a few have been discovered in it, mostly at the centres of the great concretions which it contains. The gigantic placoderm, Dinichthys hcrzcri, Newberry, was first found in these concretions. Though dating back almost to the first appearance of fishes, Newberry has shown that its nearest relationship is with the Lcpidosircn of the present day, which zoologists unite in counting as the highest of the entire class. The shale is undoubtedly the source of the natural gas and petroleum of north-eastern Ohio. The Wamrly group, which occupies about 7000 square miles of the surface of the State, is in all respects an important formation. It consists of the Bedford shale, the Berea grit, the Berea shale, the Cuyahoga shale, and the Logan group. The Berea grit has unusual geological interest. Its outcrop is a shore-line across the entire State, and it marks with perfect distinctness the eastern limit of the Cincinnati axis at this date. It is everywhere a quarry stone. The Berea stone and the Amherst stone of northern Ohio and the original Waverly stone of the lower Scioto valley belong to this horizon. In strength, durability, beauty, and the economy with which they can be worked, they stand at the head of the building stones of the State, the value of the annual products of these quarries exceeding $1,000,000. The stone is distributed as far east as the seaboard, and as far west as Duluth. Some of it has even found market in England. The Berea grit is the reservoir of the gas and oil distilled from the underlying shales, and it is also the great source of salt water for Ohio. Another building stone of great excellence and beauty comes from the base of the Cuyahoga shale in southern Ohio, the Buena Vista stone of the Ohio valley. 1 The Carboniferous Conglomerate and the Coal-measures have an aggregate thickness of at least 1500 feet, and cover more than 10,000 square miles of the surface of Ohio. The beds of coal, iron- ore, fire-clay, limestone, and cement rock that they contain render insignificant the contributions made by all other formations to the mineral wealth of the State. The Lower Coal-measures, which are here made to include the Conglomerate group of coals of Pennsyl vania, contain the seams of coal enumerated below, which are dis tributed through 500 to 800 feet of strata. The names of the seams that are used in the Pennsylvania scale are adopted here. 13. Upper Freeport coal 11 10 6. Brookville co 5 Tionesta al 6 11. (Upper Kittaiming) 10. Middle Kittaiming ! . . . . . 9 4. Upper Mercer 4 g 9. Lower Kittaiming 8 2. Quakertown 2 8. Clarion Upper ) 1. Sharon coal 1 7. Clarion Lower All these coals belong to the bituminous division. Thus far they are almost entirely worked in level free mines, and very little is taken from seams less than 3 feet in general thickness. The average thickness in the important fields is 5 feet, and the maximum (a small area of a single district) 13 feet. All of the seams enumerated above are worked, but they have very unequal values. The Middle Kittaiming seam is by far the first. The Upper Freeport ranks next in value. The Sharon coal is the most valuable in proportion to its area, furnishing, in fact, the standard of comparison for the open-burning coals of the entire Alleghany field. Both it and the Middle Kittaiming seam are used in the raw state in the manufacture of iron, a fact which sufficiently attests their purity and general excellence. In the remaining divi sions of the Coal-measures there are 10 or 12 additional seams that are of workable thickness at some of the localities in which they occur, but, with one notable exception, these seams are less steady and reliable than those of the lower measures. The exception is the Pittsburg coal, which is, all things considered, the most im portant seam of the entire coal-field to which it belongs. It is especially valued as a gas coal, and for the production of steam. Its northern outcrop passes through nine counties, with an approxi mate length of 175 miles, not counting the sinuosities. The area commonly assigned to it in Ohio exceeds 3000 square miles, but the seam has been proved for only a small fraction of the area claimed. In the production of bituminous coal in the United States Ohio ranked third in 1880, the output for that year being about 6,000,000 tons, but the production is rapidly increasing, and the State inspector of mines reckoned the output in 1882 at 8,000,000 tons. Iron ore is worked at many horizons in the Coal-measures, in seams ranging from 6 inches to 19 feet in thickness. The char coal iron of the Hanging Rock district of southern Ohio is chiefly applied to the highest uses, as the manufacture of car -wheels and castings for agricultural and other machinery. Of the 99 fur nace-stacks that now stand in Ohio, almost all depend in part, and about half depend entirely, on native ore. The amount mined annually exceeds 500,000 tons. In iron and steel industries Ohio ranks next to Pennsylvania, the value of the annual product being 35,000,000. The clays of the Coal-measures are the basis of a large and rapidly growing manufacture of stone and earthen^ware. Ohio now produces one-third of the total product of the United States. In connexion with the salt production, which is large, about half of the bromine of the world is produced in Ohio. The brine of the Tuscarawas valley yields nearly 1 lb of bromine to 1 barrel of salt. Three-fourths of Ohio are covered with the various deposits of the Drift period, which consists of "till" or boulder clay, and of the stratified sands and clays of the later stages of the period. These deposits sometimes have a thickness of 300 feet, their average in north-western Ohio being not less than 50, and in central Ohio not less than 25 feet. In the regions which they cover they exercise a controlling influence upon the relief, drainage, soils, and water- supply. They have filled the valleys of earlier drainage systems, and in many cases have obliterated all traces of their existence. The till is filled with boulders of northern origin derived from the highlands of Canada and from intervening districts. Blocks of large size are sometimes found, some of them showing 2000 cubic feet above ground. In many instances they can be referred by their mineralogical characters to particular localities, or even to particu lar ledges, from a score of miles to 400 miles distant. The stratified Drift contains vast accumulations of sand, gravel, and clay, all of <reat economic value. Brick clays of good quality are everywhere accessible. The terminal moraine that forms the boundary ot the 1 In the total value of quarry products Ohio ranks first among the States, more than 2,500,000 being reported in the census of 1880.
