Bellefontaine in the west-central part. There are no marked irregularities in the surface except the trenches out by the rivers, the Ohio River valley being lined with bluffs which in some places are 600 feet high. As noted above, the State is divided into two drainage basins. The northern portion is drained into Lake Erie by a number of streams which are all short except the Maumee, which flows through the northwestern part of the State from Indiana. The southern and much larger slope is drained into the Ohio River, some of whose tributaries in this State are of considerable size. These are the Muskingum, Hocking, Scioto, and Little and Great Miami. The Muskingum is the longest river flowing wholly within the State, and is navigable for nearly 100 miles. The Ohio itself is navigable throughout its length on the boundary, a distance of 436 miles. The other rivers of the State are chiefly important for water-power, some of them being very swift.
Climate. The climate is in general pleasant and healthful, though variable, and subject to great and sudden changes of temperature. The mean temperature of the State for January is 26°, and for July 73°. The maximum may reach as high as 108° and the minimum 34° below zero, but extreme heat or cold is never very prolonged, on account of the variable winds. The southern half is the warmer, the heat of the northern portion being tempered by the presence of Lake Erie. In the north the winters are more severe, though seldom very rigorous in any part of the State. The average annual rainfall is 39.35 inches, very evenly distributed through the, year, though there is a maximum in May and June.
Soil and Vegetation. In the southeastern part the soil is formed directly from the decomposition of the underlying rocks, while in the remaining area, covering nearly two-thirds of the State, it consists of glacial drift of great fertility. This soil contains a great percentage of limestone material in the west, while in the northeast it consists chiefly of clay, and is well adapted for wheat-growing. The alluvial soil deposited along the river courses is excellent for the raising of Indian corn. The extreme northwestern part of the State exhibits certain features of prairie country. The remainder was originally covered with forests, in which oak, chestnut, and maple predominated on the higher ground, and elm, beech, ash, and similar trees on the lowlands. The flora of the State partakes of the general character of the Northeastern United States and has few peculiar species.
For Fauna, see paragraph under United States.
Geology. The principal feature in the geology of Ohio is the broad fold or anticlinal whose axis extends from central Kentucky and crosses southwestern Ohio near Cincinnati, thence running northwest into Indiana, while a branch axis runs northeast toward the western end of Lake Erie. From this axis the strata dip gently in either direction, so that a broad area of Silurian rocks is exposed, covering southwestern Ohio, southeastern Indiana, and north central Kentucky, with a narrower band along the branch axis toward Lake Erie. A small portion of this area near Cincinnati is composed of Lower Silurian rocks known as the Cincinnati group. On either side of the Silurian are narrower outcrops of Devonian strata running on the one hand through central Indiana, and on the other through the whole length of Ohio a little west of the central line. The lateral outcrops of these strata along the branch axis occupy the northwestern corner of the State and a narrow belt along the entire southern shore of Lake Erie. The remainder of Ohio, including nearly the whole eastern half, consists of Carboniferous strata. The entire State seems to have been above sea level throughout the Mesozoic and Cenozoic eras, there being no formations later than the Carboniferous until we come to the glacial drift. This covers about two-thirds of the State, leaving the southeastern portion untouched by the ice invasion. The drift deposit is in some places several hundred feet thick, and consists of alternating layers of boulder clay, stratified sand, finely laminated clay, sandy clay, and gravel. Raised beaches showing the former extent of the Great Lakes have been traced through the State, and another interesting feature of the surface are the deeply carved river-valleys which are completely filled with débris, so that the rivers sometimes flow far above their former beds.
Mineral Resources and Mining. Both the upper and lower coal measures contain several workable seams interbedded between strata of shale, limestone, sandstone, and clay, and ranging in thickness from two to over a dozen feet. It has been estimated that Ohio contains enough coal to supply the demand of the State for soft coal for 1000 years at the present rate of consumption. The interbedding strata of the coal measures yield fire-clay and building stone, and here also are found the iron ores of the carbonate variety. The Salina group of the Silurian strata near Sandusky contains valuable gypsum deposits, and salt deposits also occur at various places. One of the most remarkable events in the mineralogical development of Ohio was the discovery in 1884 of petroleum in the Trenton limestone formation of Lower Silurian age. This formation as well as the Upper Silurian inclosed also considerable reservoirs of natural gas.
Ohio's output of coal increased from about 6,000,000 tons in 1880 to 13,562,000 tons in 1892. It did not exceed this figure again until 1898. In that year and in the two following years the increase was very rapid. The output in 1900 aggregated 18,988,150 short tons, amounting to 7 per cent. of the total output for the country. It was valued at $19,292,246. Only a small amount of the coal output is used in the production of coke. The average number of employees engaged in the coal industry in that year was 27,628.
The petroleum development has been of recent date. Little had been produced prior to 1885, which year marks the beginning of the swift progress of the industry. The yield increase from 90,081 barrels in 1884 to 661,580 in 1885, 10,010,868 in 1888, and 23,941,169 in 1896. The last is the record year. The output for 1900 was 22,362,730 barrels, valued at $24,091,601. This was much in excess of that of any other State, and was over one-fourth of the total output for the United States. The petroleum is obtained in two sections of the State, the southeast and northwest. The former is known as the Eastern district, and the latter—the more important—as the Lima district. In a third region, known
