_Geology._--The county presents a remarkable simplicity of geological structure. Its surface is controlled throughout by the "Hercynian" folds, running from the Kerry border eastward to the sea at Youghal. The Old Red Sandstone comes out in the north, forming the heather-clad Ballyhoura Hills, which are repeated across the limestone hollow of Mitchelstown by the western spur of the Knockmealdown Mountains. On the west, beds as high as the Millstone Grit and Coal Measures remain above the limestone, extending from Mallow and Kanturk to the Limerick and Kerry borders. Another synclinal of Carboniferous Limestone runs from Millstreet through Lismore, and the Blackwater has worn out an easy course along it. Then the Old Red Sandstone again rises as an undulating upland through the centre of the county, with a few synclinal patches of Carboniferous Shale and Limestone caught in on its back. Cork city lies on the north slope and in the floor of a larger synclinal, and the Yellow Sandstone, which forms the passage-beds from the Old Red Sandstone to the Carboniferous, appears near the city. This hollow continues across the Lee through Middleton. The limestone in it has become crystalline, veined and brecciated, while a fine red staining, especially at Little Island, adds to its value as a marble. After another anticlinal of Old Red Sandstone, the Carboniferous Slate occupies most of the country southward, with occasional appearances of the basal Coomhola Grits and of the underlying Old Red Sandstone along anticlinals. The soils thus vary from sandy loams, usually on the higher ground, to stiff clays along the limestone hollows.